Takeuchi Hydraulic excavator TB1140 (Serial No. 514400002~). Operator's Manual

3. DESCRIPTION OF FUNCTIONS

Grip pattern

1. Download: Used to down-

load the settings to the con-

troller.

2. Upload: Used to upload the

current settings from the

controller.

3. Reverse the switch opera-

tion (A) and (B) for the 1st

auxiliary line piping.

4. Set the detent mode target

to switch operation (B).

5. Reverse the switch opera-

tion (C) and (D) for the 2nd/

4th auxiliary line piping.

Changing the switch pattern

DANGER

Make sure to read the instruction manual for the switch pattern switching kit before attempting the work.

After changing the switch pattern, make sure to affix the decal sticker for the switch pattern switching kit in the specified

location.

a. Click on (2) to pull up the current setting conditions.

b. Select the checkboxes for the items to be changed.

c. Click on (1) to download the items set in b. to the controller.

3. DESCRIPTION OF FUNCTIONS

6S1AS01

3. DESCRIPTION OF FUNCTIONS

Misc

1. Download: Used to down-

load the settings to the con-

troller.

2. Upload: Used to upload the

current settings from the

controller.

3. Change the wiper interval.

4. Return all settings other than

the hour meter settings back

to their initial values (factory

default settings).

Changing the interval

a. Click on (2) to pull up the current setting conditions.

b. Click above or below (3) to set the option setting to any desired value.

c. Click on (1) to download the value set in b. to the controller.

Initialization

Click on (4) to return controller settings except for the hour meter settings back to the factory default settings.

3. DESCRIPTION OF FUNCTIONS

6S1AS01

3. DESCRIPTION OF FUNCTIONS

Lift alarm

1. Download: Used to down-

load the settings to the con-

troller.

2. Upload: Used to upload the

current settings from the

controller.

3. Set pressure for the lift alarm

Changing the set pressure for the lift alarm

WARNING

Exercise adequate caution when changing the set pressure for the lift alarm. The machine could topple over when the

pressure is changed.

a. Click on (2) to pull up the current setting conditions.

b. Click above or below (3) to set the option setting to any desired value.

c. Click on (1) to download the value set in b. to the controller.

3. DESCRIPTION OF FUNCTIONS

6S1AS01

AIR CONDITIONER SYSTEM(RED DOT)

Overview of System Operation

• Truck and Heavy Equipment Systems

• Air Conditioner-System Operation

• Heater System Operation

• Environmental Effects on System Operation

• Chapter Review

Truck and Heavy Equipment Systems

A variety of HVAC systems are in use today, some old and some new. There are:

• Vehicle manufacturer installed systems

• Owner specified systems

• Add-on systems

• Retrofit systems

The system components come in different colors, shapes, and sizes. They may be

mounted in or on the cab in varied locations. Owners or fleet maintenance people can

modify systems by adding controls, auxiliary units or ducts. Major components are

sometimes replaced due to damage or failure. All systems were, at least originally,

designed and installed to meet the needs of an operator. Figure 2-1 includes illus-

trations of various AC and Heater systems. They illustrate system advantages and

disadvantages explained in the paragraphs that follow.

The HVAC system includes both heater and air conditioner components, usually

a common control, and air ducts. The system cools the cab by removing heat energy.

It removes moisture from damp air in the cab and adds fresh outside air to the cab. In

this way, the operator can work comfortably in all kinds of weather.

A sleeper unit, built in or added on, increases the air volumes in the cab. The air

conditioner or heater must circulate and cool or heat a larger amount of air. This is ac-

complished by routing ducts and controls to the sleeper compartment as part of system

design. Components may be increased in size to handle the larger cab air volume. A

bigger heater core, air conditioning evaporator coil, condenser, blower or fan may be

included. Often, on long haul trucks, auxiliary air conditioning and heater components

and controls are added. The objective remains the same, to move heat energy and

maintain occupant comfort.

System Operation

Air Conditioner—System Operation

We have described the movement of heat energy and basic HVAC system function in

Chapter 1. Now we will go into some detail on how an air conditioner operates. The

system is sealed to keep out air and moisture. To operate properly, the inside of the

system contains a measured amount of refrigerant and special refrigerant oil that keeps

the system lubricated. Figure 2-2 is an illustration of system components without the

cab outline, in-cab controls, component housing, and air ducts or vents. Please study

it for a moment. Note the information printed next to each component. Remember that

the components may be positioned and attached to the truck in various locations.

Air Conditioner—System Operation

The following AC components are discussed in detail in this section:

1. Compressor/Clutch Assembly

2. Condenser

3. Receiver-Drier

4. Expansion Valve

5. Evaporator Coil

Figure 2-2

Air Conditioner components

are connected together to

illustrate system operation.

The components shown are

not to scale. The refrigerant

and refrigerant oil are clear

in color and not visible in

this drawing. The small ar-

rows inside the components

and connecting hoses show

the direction of refrigerant

flow (refrigerant circuit).

1. Compressor/Clutch Assembly

The compressor/clutch assembly is the heart of the system. When the clutch is engaged,

the compressor pumps refrigerant and oil around the system. It raises the temperature

and pressure of the refrigerant gas, and forces it to the condenser where it changes

state and becomes a liquid. The compressor also sucks the vaporized refrigerant out

of the evaporator and back inside itself in the form of gas. One way valves inside the

compressor separate the compressed gas (high pressure) side of the system from the

suction (low pressure) side. Figure 2-3 shows a cutaway view of a compressor with the

high and low pressure sides noted.

System Operation

Figure 2-3

The compressor inlet is

low pressure and the outlet

is high pressure. The reed

valves are one way. They

open to allow refrigerant gas

to enter the compressor on

the down stroke and exit on

the upstroke. Note the open

valves in the illustrations.

The clutch is mounted on the shaft of the compressor and is engaged by electromag-

netic action. Part of the clutch assembly is an electromagnetic wire coil. The coil is

energized through a thermostat that senses the temperature in the evaporator coil. If

the evaporator is too warm the electrical contacts close and allows power to flow to the

clutch. The compressor shaft is engaged and moves the refrigerant around inside the

system. Figure 2-4 is a cutaway view of the clutch mounted on the compressor.

Figure 2-4

The clutch shown here has

its electromagnetic coil

mounted on the compressor

body. When the coil is ener-

gized, magnetic force pulls

the clutch drive plate into

the pulley. This action locks

the pulley to the compressor

drive shaft and drives the

compressor.

2. Condenser

The refrigerant gas leaves the compressor and moves through a high pressure hose to

the condenser. Inside the condenser the gas “changes state” and becomes a liquid. It

is still hot and under pressure. Remember in Chapter 1 when we talked about water at

212 degrees Fahrenheit? Heat energy was involved in the “change of state,” but the

temperature did not change. The same kind of action happens inside the AC system.

The refrigerant gas gives up a lot of heat energy to the outside air as it “changes state”

in the condenser. Figure 2-5 illustrates a condenser. Air moving through the condenser

absorbs heat from the refrigerant. The amount of air flow through the condenser is the

major factor in how well the condenser functions.

Air Conditioner—System Operation

Figure 2-5

As the refrigerant gas moves

through the tubing coil from

top to bottom, it condenses

(changes state) into a liquid.

For ease of installation,

condenser fittings are often

routed close together.

3. Receiver-Drier

The liquid refrigerant continues to move inside the system, out of the condenser

through a tube or hose to the receiver-drier. The receiver-drier serves as a small stor-

age tank and filter for the refrigerant. It is also a good location to mount pressure

switches and often contains a sight glass (small window) used to view activity inside

the system. The receiver-drier, Figure 2-6, also separates gas (bubbles) from the liquid

with a pick-up tube as shown in this illustration. Some receiver-driers have a spring to

preload the desiccant pack.

Figure 2-6

This cutaway view of a re-

ceiver-drier shows the filter

elements, inlet, outlet and

refrigerant path. The sight

glass is a small window into

the system used in diagnosis

and when adding refrigerant

(charging the system).

System Operation

4. Expansion Valve (Refrigerant Metering Device)

When refrigerant moves from the receiver-drier, it travels through another high pres-

sure hose to a metering device at the inlet of the evaporator coil. The metering device

can be an expansion valve, an expansion tube or a combination (multiple function)

valve. Between the compressor and this point inside the system, the pressure is high

and can range from 150 to 250 pounds per square inch. The expansion valve (TXV) is

closely connected to the evaporator. A diaphragm opens the valve by exerting pressure

on the spring. Pressure comes from gas inside the diaphragm housing on top of the

valve and in the sealed sensing bulb. The sensing tube is located in the outlet of the

evaporator and picks up heat from warm refrigerant leaving the evaporator. The gas in

the valve diaphragm housing and sensing tube expands when it gets warmer and forces

the expansion valve open at the metering orifice.

Figure 2-7

This block type expansion

valve cutaway view will

give you a better idea how

these valves work. Spring

pressure holds the valve

closed.

5. Evaporator Coil

The expansion valve or other type of metering device bleeds high pressure refrigerant

into the evaporator coil, where the pressure is low. The refrigerant expands rapidly in

this low pressure environment. When it expands it “changes state”. The sudden drop

in pressure brings the refrigerant temperature down quickly inside the evaporator coil.

Figure 2-8 shows an evaporator coil and thermostat. Refrigerant is sprayed into the

evaporator by the high side pressure when the expansion valve opens. The refrigerant

absorbs heat from the air when the blower forces the air through the fins. When the

thermostat probe senses the upper limit of the thermostat heat setting, a circuit closes.

The compressor clutch engages and the compressor operates and moves more refriger-

ant to the high side of the system.

Air Conditioner—System Operation

Figure 2-8

The evaporator coil as

shown is of fin and tube

construction. The thermostat

probe is positioned in

between the evaporator fins

and senses the temperature.

Note: Moisture in the air (humidity) condenses on the fins of the evapo-

rator as water droplets which drain out of the evaporator through

a drain hose. This action dehumidifies the air in the cab as part of

system operation, and contributes to operator comfort.

Cab air forced across the evaporator coil gives up heat energy to the cold refrig-

erant inside the coil. The cooled air circulates in the cab for occupant comfort.

Refrigerant continues to expand and absorb heat energy in the evaporator coil.

Refrigerant changes from liquid to gas before it leaves the evaporator on the way

back to the compressor. The refrigerant gas moves to the compressor through a

low pressure (suction) hose. When the compressor is operating, it sucks the re-

frigerant gas back inside, compressing and raising its temperature and pressure.

Some of AC system operation is controlled by the operator, and some is automatic.

The operator can turn the system on and off, regulate the air velocity with the blower

control, and in some designs adjust the thermostat control. The system and component

operating range settings automatically cycle the clutch on and off. The operation of

the expansion valve or other refrigerant metering device at the inlet to the evaporator

is automatic.

Individual system features may differ, but the basic system function remains the

same. Variations in components and controls are described in Chapters 4 and 5. The

engine provides the power for both air conditioner and heater operation. It drives the

AC compressor and the cooling system water pump. Engine RPM affects the efficiency

of both the heater and air conditioner. The slower the engine RPM, the less capacity a

heater or AC system will have.

When an AC system is operating, the high pressure side com-

WARNING

ponents, fittings and high pressure lines or hoses can be hot

enough to burn your skin if you touch them. This includes the

compressor, clutch, hoses, condenser, receiver-drier, and any

control devices or metal tubing. The low pressure side will be

cool to the touch. In operation the AC system is under load

and high side pressures normally range between 150 and 250

pounds per square inch for R-12 and higher for some other

refrigerants.

System Operation

Heater System Operation

Heater and air conditioner systems both have the same basic function of moving heat.

They take advantage of nature’s laws where heat energy always moves from a warmer

to a cooler area. In a heater system there is no “change of state” involved in system

operation. The system is sealed and operates under pressure, but the pressure is low

when compared to an air conditioner.

A heater system uses the engine coolant to carry excess heat energy to the cab air.

The heart of the system is the water pump. The water pump forces hot coolant through

a hose from the engine block and through the heater core. The coolant is returned to the

engine cooling system either at the suction side of the water pump or to the radiator.

The heater fan or blower forces cab air through the heater core where heat energy

moves from the engine coolant to the air in the cab. Figure 2-9 illustrates the main

heater system components. In-cab controls, component housing and air vents are not

shown.

The following heater components are discussed in detail in this section:

1. Heater Core

2. Water Valves

3. Defrosters and Ducts

4. Blowers and Fans

Figure 2-9

This view of a heater system

shows the main components

and how they are connected.

Additional heater controls, ducts, air vents, blend-air doors, temperature regulating

devices and auxiliary heaters may be installed as part of a heater system. These may be

air, vacuum, electrical or mechanically operated.

Environmental Effects

1. Heater Core

Heater cores are like small radiators. The fin and tube construction is designed to

route coolant flow for the best possible heat energy transfer from coolant to cab

air. Hoses from and to the engine are connected to the core with clamps. The core

outlet may be larger or the same size as the inlet.

2. Water Valves

Water valves may be cable, vacuum or air controlled. The valve can be either

open, closed or set part way open. Some valves have a bypass design to return

coolant to the engine. Most are manually controlled although electronic systems

are now being installed.

3. Defrosters and Ducts

Defrosting is accomplished by directing heated dry air through ducts to the

windshield. The heater system serves the dual purpose of defrosting and heating.

Controls are used to route the air flow to the windshield and occupant areas by

opening and closing duct doors. Controls may be manual, air or vacuum.

Many vehicles use a “defrost interlock” system which utilizes the air condi-

tioner to dry the defrost air and clear the cab windows more quickly.

4. Blowers and Fans

Blowers or fans are used in the system to move cab air through the heater core

and evaporator. Air can be pushed or pulled through the core depending on sys-

tem design. Blower or fan speed is usually selected by the operator.

Environmental Effects on System Operation

The environment outside the cab involves more than the weather. It may be hot and

humid or cold and dry. That is only part of the condition the HVAC system must handle

to maintain an ideal comfort range. A truck can be at idle, in traffic or moving along

for hours on the Interstate at 65 M.P.H. The load condition on a trip can include going

out full, coming home empty, or driving across the Rockies or Kansas plains during

the day or night. The truck color and shape, the windows and angle of the sun are all

variables that can increase or decrease the “load” on the system. The following are a

few examples of environmental effect:

• A black cab-over (COE) with a dark color interior will be more dif-

ficult to cool than the same vehicle with white paint and a light colored

interior. The black cab picks up and holds the radiant heat from the sun

more easily than the white one.

• In Florida or Houston the humidity in mid summer can be very high

with the temperature in the high 90’s or low 100’s. The AC unit must

remove a lot of moisture from the air in the cab as the air moves through

the evaporator fins. The more moisture on the fins, the less effective the

transfer of heat is to the refrigerant inside the evaporator coil.

System Operation

• On a cold day the temperature can drop below zero. The engine may

run cooler so the engine coolant is cooler when it circulates through

the heater. The heat in the cab moves out of the cab faster (remember

heat always moves to a cooler area until both are the same tempera-

ture—nature’s law). To maintain cab comfort you have to increase the

flow of coolant through the heater, increase coolant temperature, and/or

move more air through the heater core.

• On a hot day, an off-road vehicle experiences cooling at a slower rate

than an on-road vehicle. This is a result of high sun-load, large window

area and often less insulation.

It is important for you to keep environmental effects in mind when you are servicing

or diagnosing heater or air conditioner systems. If you work in Denver the altitude will

affect system function and pressure. In Houston the heat and humidity may lower heat

transfer to the air at the condenser and increase system operating pressures.

Chapter Review

•

HVAC systems range from simple cab heaters to multi-function com-

bination systems. The multi-function system can heat and cool the cab

and sleeper unit, and have separate auxiliary components and controls

for driver and passenger comfort.

•

Both heater (engine) coolant and air conditioner refrigerant circulate

inside sealed, pressurized systems. The normal air conditioner operat-

ing pressure ranges from 150 to 250 pounds per square inch, sometimes

higher with a different refrigerant.

•

Air conditioners have a high and a low pressure side within the system.

The compressor is the starting point of the high side. Pressure drops at

the expansion valve opening to the evaporator.

•

The basic components of an AC system are the compressorclutch as-

sembly, high pressure lines, condenser, receiver-drier, expansion valve,

evaporator, thermostat, blower assembly, and suction lines. There may

be other controls installed for more complex systems.

•

The basic components of a heater system are the inlet and outlet hoses,

a water valve and valve control, heater core and fan or blower assembly.

There may be other controls for more complex systems.

•

An air conditioner system uses the “change of state” of refrigerant inside

the system to move heat from the cab air to the outside air. Refrigerant

changes from a gas to a liquid in the condenser, and back to a gas in the

evaporator.

•

A heater system uses the heat from the engine, carried to the heater core

by the action of the water pump, to warm the air in the cab. There is no

change of state within the heater system.

•

Environmental conditions affect how both heaters and air conditioners

work. Weather, driving conditions, color of the vehicle are factors. All

contribute to heat gain or loss inside a cab and how much heat energy

must be moved to maintain occupant comfort.

Inspection and Maintenance-

without gauges

• Discussion of Inspection & Maintenance Survey Results

• Visual Inspection - System Off

• Electrical System Inspection

• Performance Inspection - Engine Running

• Heater System Inspection

• Preventive Maintenance Worksheet

• Chapter Review

Discussion of Inspection & Maintenance Survey Results

There are three reasons for regular inspection and maintenance procedures:

1. They save money in the long run by reducing down time and often

prevent more costly repairs.

2. They help to insure driver comfort and safety.

3. They add to your store of knowledge about these systems and main-

tain your level of efficiency.

About half of all heavy duty vehicles have air conditioners. Surveys of AC system

owners find that over 30% of the systems are serviced every six months or less, and

another 62% are serviced at least once a year.

The survey also covered how often the different components required maintenance.

Figure 7.1 below shows survey finding percentages. Failure of any of the AC compo-

nents listed in the survey could cause a system to malfunction or stop cooling.

INSPECTION & MAINTENANCE SURVEY

Figure 7-1

This chart shows mainte-

nance frequency, lists key

parts and how often they

require maintenance.

Note: The above survey results may not apply to your situation. Actual

operating conditions for the vehicles you service will determine

or influence maintenance frequency and requirements.

The following inspection procedures should take about 15 to 20 minutes, longer if

corrective steps, part replacement or adding refrigerant is necessary. There is a “Pre-

ventive Maintenance Worksheet” you may use at the end of this chapter, Figure 7-9

Inspection & Maintenance

Visual Inspection - System Off

Your observations and the corrective measures you take may be different depending

on circumstances. The following inspection procedures are explained in more detail

below:

1. Observe the System

2. Inspect Parts

3. Check Hoses and Fittings

4. Check for Refrigerant Leaks

Use the following procedures as a general rule in performing a visual inspection with

the AC system off:

1. Observe the System

Your first inspection step is to answer the following question if you can:

• Has the vehicle just come in off the road and has the HVAC system

been in use?

• Did the operator or work order explain or describe any problems

about the system?

• Did someone else work on the system yesterday, 700 miles down the

road? Your first inspection step is to answer these questions if you

can.

Even when someone has told you what is wrong with an HVAC

CAUTION

system, you should perform a visual inspection. Always make

a visual inspection before you hook up the manifold gauge set.

Never add refrigerant to a system until you have made a com-

plete visual and performance inspection.

2. Inspect Parts

Look at the system for what might come loose, leak, wear out or become dirty

and not function the way it should. The main points for visual inspection of the

system are emphasized in Figure 7-2.

Visual Inspection

Figure 7-2

This system illustration

notes the main points for

visual inspection.

A. Condenser - Is it free of leaves, bugs, bird feathers or mud? The condenser must

be relatively clean to work well as a heat exchanger. How you clean the condenser

depends on where it is mounted. The condenser fin comb, air hose and nozzle, or

soap and water may be used. Where possible, check condenser mounting bolts or

screws and tighten them if necessary.

Condenser failure often results from loose hoses. Hose movement will cause

fatigue failure of condenser tubing adjacent to the fittings. Make sure the hoses are

securely clamped.

While inspecting the condenser check the receiver-drier sight glass and connec-

tions. Look to see if the sight glass has a moisture indicator that is showing moisture

in the system.

B. Components Under the Hood - Tip the cab or raise the hood. Look at the

compressor mounting bracket, compressor clutch assembly, drive belt and pulley

alignment. The mounting bracket, compressor, clutch and drive pulley should be

fastened securely, and a clutch groove (there may be two groves) should be in line

with the drive pulley. Tighten all bolts shown in Figure 7-3, as you inspect.

Figure 7-3

Engine and compressor

vibration can work mount-

ing bolts loose. Tighten

all mounting bolts as you

inspect the system. Slots in

the mounting bracket are

used to move the compressor

clutch assembly in order to

adjust belt tension or align-

ment.

Inspection & Maintenance

C. Drive Belt - The drive belt should be tight and in good condition. Use a belt ten-

sion gauge to check tension (120 pounds maximum). With experience, you can feel

belt tension by twisting the belt. Try feeling belt tension after using the gauge, when

you know the tension is correct. Replace belts if they are frayed or look worn.

If the clutch pulley/belt alignment is obviously off, you need to loosen the com-

pressor or mounting bracket, or both—and use the alignment bar to line up the clutch

pulley with the drive pulley. Tighten compressor mounting bolts first, then the bolts

holding the bracket. The mounting bracket should have slots or other means of

adjustment to allow you to adjust the tension of the drive belt. When you use a pry

bar to apply tension, be sure you do not pry against the compressor. Pry against the

mounting bracket.

3. Check Hoses and Fittings

Check all hoses and fittings. Look for places where hoses flex when the cab is tilted.

Any places the hoses or fittings are fastened, clamped, connected, bent or secured are

potential wear points. This also applies to places where hoses are not clamped or sup-

ported but should be (often near the condenser). All of these spots are potential leak or

damage points. Tighten, re-fasten, add, or replace as indicated by your inspection.

4. Check for Refrigerant Leaks

System refrigerant leaks can be anywhere but there are obvious places. You can spot

some by looking for signs of refrigerant oil forced out with refrigerant leakage. One

location leaks frequently occur is the compressor shaft seal. The shaft and seal are

hidden behind the clutch assembly, but centrifugal force will throw the oil off the

shaft and against the engine, bracket or whatever is close. Check these points when

you examine the compressor clutch and mounting bracket. A solution of soap and

water applied around potential leak points works well for detecting leaks. A leak in the

evaporator may be indicated if you feel around the condensate drain hole and find oil

present.

Note: You can add inexpensive dry nitrogen gas to the system instead of

R-12 if system pressures are low. Dispense the gas at no more than

200-250 PSI as this is sufficient pressure to cause or indicate a leak

point in the AC system. AC service procedures for complete system

recovering of refrigerant, evacuating, and recharging are covered and

illustrated in

Note: A leaking heater core could also result in coolant at the condensate

drain.

Electrical System Inspection

You can feel for oil at the bottom of all connections (see Figure 7-4) if the system

is not too hot. Of course, a few minutes with an electronic leak detector is the

best way to check for leaks. Keep in mind that pressure is different in a system at

rest, so small leaks may be hard to find. Pressure in a system at rest, will equalize

at from 60 to 95 PSI, depending on outside air temperature. This means there is

more pressure in the low side of the system at rest than during normal system

operation. Just the opposite is true of the high side; at rest, high side pressure is

lower. You may want to use the detector to check for leaks in the high side when

the air conditioner is operating, if you suspect a leak and can’t find it when the

system is at rest.

Figure 7-4

This illustration shows a po-

tential refrigerant leak point

at the condenser fitting.

Electrical System Inspection

The two stages of an electrical inspection are explained in more detail below:

1. Inspect Electrical Connections

2. Check Electrical Current Flow and Device Functions

Use the following procedures to perform an electrical system inspection:

1. Inspect Electrical Connections

First, while you are making your visual inspection under the hood (cab) and/or at

the roof top condenser, take a moment and check all electrical connections visu-

ally and by feel. Look for any corrosion on leads or connectors and clean them.

Make sure all leads and wires are properly supported and securely connected.

2. Check Electrical Current Flow and Device Functions

Perform the following steps to check current flow and electrical device func-

tions:

A. Turn the Ignition On - To check current flow the ignition must be on.

Inspection & Maintenance

B. Turn the AC System On - This will power the thermostat and clutch.

If it does not come on, use the AC mode switch to check the leads to the

switch. You should be able to hear a “click” from the thermostat and hear

the clutch drive plate “snap” against the clutch pulley. You can not check

thermostat cycling on and off until you do the performance inspection. Fig-

ure 7-5 illustrates a typical AC electrical system and the places you should

inspect.

Figure 7-5

The electrical system inspec-

tion points are noted with

check marks (✔) on this

wiring diagram (electrical

schematic).

C. Check Fuses - If there is a failure and you have made sure all con-

nections are clean and tight, you need to check fuses—in-cab as well as

in-line.

D. Check Clutch Engagement - Since you can’t see and may not hear the

clutch engage, get out and look at the clutch. If it’s engaged, you will see

that the drive plate is against the pulley and not slightly spaced from it. If

you are not sure the clutch is engaged, look for the lead wire connector near

the clutch. Break and close that connection. The clutch will disengage and

engage again.

E. Test Blower Speed Operation - Some systems have a common switch

that turns on the air conditioner and powers the blower motor. Test blower

speed operation by adjusting this or the separate blower control switch.

Feeling the air flow from the ducts or note blower sound (speed) changes.

F. Inspect Roof Mounted Condensers - Don’t forget to inspect roof

mounted condensers and AC systems for dirt and debris. Be sure the con-

denser fan(s) are working properly and all parts and electrical connections

are securely fastened. The roof mounted condenser fans may come on when

the system is turned on. Like the thermostat and most clutches, the normal

on-off cycling action can not be observed until the engine is running with

the AC system on.

Electrical System Inspection

Performance Inspection - Engine Running

The purpose of visual and electrical inspection is to detect obvious problems and assure

AC system function for an accurate performance inspection. If you do the performance

inspection first, you could be mislead. Problem areas discovered during the perfor-

mance inspection can give you false clues or symptoms, and result in repair errors and

come-backs. The following performance inspection procedures are explained in more

detail below:

1. Inspect System Component Cycling and

Cab Temperature Levels

2. Check Clutch Cycling Under Load

3. Check Sight Glass

The performance inspection does not cover pressure and temperature sensitive safety

devices (cutout switches, fan control, Trinary etc.). Testing these devices requires the

use of the manifold gauge set for observation of internal system pressures during tests.

These are explained in

Use the following procedures as a general rule in a performance inspection:

1. Inspect System Component Cycling and Cab

Temperature Levels

A. Turn On the Engine and Air Conditioner - Inspect for system compo-

nent cycling and cab temperature levels.

Note: System performance testing will be much faster if all doors

and windows in the cab are closed.

The cab air must cool down to thermostat control setting lev-

els before system components will cycle on and off, indicating

correct function. This is called ‘stabilizing the system’ and takes

about five minutes of operation. In very hot weather the system

may not cycle.

B. Check Thermometer Readings - In the cab you can use your thermom-

eter to measure air temperature at the vents. When the evaporator is easy to

reach with a thermometer probe without removing some of the dash or duct

work, use the probe to measure evaporator temperature. When the AC unit

is on and working correctly, you can see the thermometer dial needle move

down to about 32 degrees, then rise six to ten degrees and move back down

again. The movement up and down indicates that the cycling clutch and

thermostat, or orifice tube and accumulator pressure switch (to the clutch)

are functioning correctly. In systems with a non-cycling clutch, this move-

ment indicates correct function of the refrigerant metering device.

The needle movement is called “temperature swing.” When you can ad-

just the thermostat setting, the range of swing should change. For example,

from full cooling (cold) to moderate (between cold and warm), the swing

may change from 32-38 to 32-42 degrees.

Inspection & Maintenance

These readings at the vents will be higher and temperature swing slower

and not as obvious. Also blower speed will cause the temperature, levels to

read higher (high air speed) or lower (low air speed) at the same thermostat

setting. When you measure air temperature, an electronic thermometer/py-

rometer is a great tool to have. You can easily measure cab air temperature

at several locations quickly.

Swing temperatures vary depending on where you measure temperature,

and on outside temperature, humidity and altitude. The chart in Figure 7-6,

shows some examples of typical temperature variables. Don’t forget that

cab and sleeper area temperatures can vary within the same vehicle. Also,

electronic controls used in newer HVAC systems often keep the tempera-

ture spread within a narrower range.

Figure 7-6

air temp.

70°

80°

90°

100°

degrees f.

The chart of AC system and

cab temperature range shows

air quality

humid

dry

humid

dry

humid

dry

humid

dry

you typical variables.

center outlet

43°

40°

44°

40°

47°

40°

52°

41°

air temp.

degrees f.

47°

44°

48°

44°

51°

44°

56°

45°

left & right air outlet temperature will vary

left

right

left

right

left

right

left

right

outlet air temp.

40°

41°

43°

46°

47°

48°

50°

range degrees f.

41°

44°

45°

47°

52°

54°

55°

56°

2. Check Clutch Cycling Under Load

The following operating inspections, visual and by feel, are done outside the cab

while you wait for the system to stabilize.

A. Lift hood - With the hood up (or cab tilted) observe the clutch cycling

under load.

Note: If the condenser is hood mounted you may not have adequate air

flow through it.

B. Touch suction and discharge lines - Soon after system start up you can

safely feel the suction and discharge lines and note their change in tempera-

ture. The discharge line will get hot (after a while it may be to hot to touch)

and the suction line will get cooler.

3. Check Sight Glass

The sight glass is the only point where you can actually see inside the air condi-

tioner during operation. Check the sight glass through the window on the top of

the receiver-drier (or the separate in-line sight glass). If the system is functioning

properly and cooling the cab adequately, the sight glass should be clear (you will

not see anything in it). If it is not clear when the system is first turned on, wait a

few minutes for the system to stabilize, then look again. Figure 7-7 illustrates and

explains what you may observe in the sight glass. Roof mounted condenser fans

may run continuously or cycle on and off. If you can’t tell by sound you may have

to climb a ladder and observe the fan blades.

Performance Inspection

Figure 7-7

These drawings illustrate

conditions you may observe

in the sight glass window.

Note: A roof mounted condenser or AC unit assembly often includes

a roof mounted receiver-drier (and sight glass) close to the con-

denser.

Heater System Inspection

A heater system inspection is really a combination engine cooling system and heater

inspection. All heater/cooling system rubber parts deteriorate due to the air (ozone),

heat, coolant and oils. They should be replaced at regular intervals to prevent break-

down on the road. Metal parts and gaskets are subject to malfunction or breakdown

due to fatigue and corrosion.

Coolant has a limited life and should be replaced regularly. If it is dirty, the cool-

ing system should be drained and flushed or back flushed (using special equipment)

before refilling with clean water and anti-freeze. Coolant must be hot when using the

hydrometer to check protection (freeze-up) level. The following inspection procedures

are explained in more detail below:

1. Check Heater Control Valve Function

2. Inspect Other Functions

1. Check Heater Control Valve Function

Many air conditioner/heater systems depend on the heater control valve for tem-

perature control and positive closure. You can easily check heater control valve

function as follows.

A. Cool engine - Start with the engine cool, set the temperature to cold and

leave the fan off. As the engine warms up, feel the heater return hose. If the

hose feels warm or hot, the heater control valve is leaking internally. This

type of leak can seriously reduce air conditioning performance.

Inspection & Maintenance

B. Warm up engine - Next, let the engine warm up to normal operating

temperature and set both fan and temperature on high. Feel both heater sup-

ply and return hoses. If there is a noticeable difference in their temperature,

it indicates a low flow of coolant through the heater core (a partially closed

or blocked heater control valve). This could result in poor heating perfor-

mance during cold weather conditions.

Figure 7-8

Heater/cooling system

potential problem areas and

checks are indicated in this

drawing.

2. Inspect Other Functions

There are some things you can’t see or feel when you inspect the thermostat,

heater core, radiator pressure cap, electrical switch and control valve functions.

Some of these can be checked with the pressure and thermostat testers as de-

scribed in Chapter 6. A hand pump pressure tester can also be used to check for

coolant leaks. This is done by using the pump to raise the pressure inside the

system above normal operating pressure to force small suspected leaks to show

up.

Heater/cooling electrical and valve component inspection is the same as air

conditioner inspection. The controls are operated to see if they function correctly

to maintain or vary cab temperature and air flow.

Preventive Maintenance Worksheet

Please feel free to modify or copy the worksheet in Figure 7-9. Actual vehicle use, mile-

age, operating conditions and maintenance budget may influence service frequency.

Chapter Review

The purpose of these brief inspection procedures is for vehicle system maintenance

and to determine if further, more detailed service is required. The uses of a manifold

gauge set, system troubleshooting, recovery, flushing, evacuating and charging are

explained in the next chapter.

High usage and operating condition variations are tough on air conditioning and

heater components. You should establish and follow regular inspection and mainte-

nance procedures to improve overall system function and component service life.

The typical inspection should not take more than 15 to 20 minutes unless com-

ponent replacement and/or complete system evacuation and recharging is warranted.

The survey results shown in Figure 7-1, indicate belts, compressor clutch assembly,

condenser and the refrigerant lines are the most frequent problem areas. However,

your own experience with service and maintenance may vary from survey results.

Inspection should first be visual and by feel. Some of your electrical system inspec-

tion will be done as you inspect other components (checking leads, connections and

for loose wires). When you check the electrical circuit, begin with the engine off but

ignition on. A system performance inspection with the engine running and system on

really combines electrical and AC or heater system function.

Troubleshooting

& Service Procedures

• Troubleshooting Overview

• Understanding System Function

• A Troubleshooting Example

• Manifold Gauge Set Installation

• Troubleshooting by Manifold Gauge Set Readings

• Review of Frequent Problem Areas

• Conclusion

Can you fix an air conditioner or heater system without finding and correcting the

cause of the problem? You bet you can! It happens every day and it’s not good for

business. Here is an example. A truck pulls in off the road and the operator asks to have

his rig serviced in a hurry. He tells you the air conditioner isn’t cooling like it should

and dashes into the restaurant for lunch.

You tip the hood, and check the sight glass on top of the receiver-drier. You see

bubbles, not a lot but a fairly constant stream of them. It is obvious the system is low

on refrigerant so you hook up the manifold gauge set, purge the gauge set hoses of

air, and add refrigerant until the sight glass clears. Then you check evaporator tem-

perature and it’s OK. The air conditioner is repaired right? Wrong! What you did is

add refrigerant and the problem went away. You did not find and fix the cause of the

problem.

Component failure in an air conditioning system may be the result of a problem

elsewhere in the system. For example, a belt or clutch failure might be caused by a

dirty condenser restricting air flow and increasing head pressures. High head pressures

commonly create problems with other system components. Take time to look beyond

the obvious for a potential hidden problem.

Troubleshooting Overview

Troubleshooting includes collecting enough information to locate the cause of the

problem, then correcting the problem and its cause by replacement, adjustment, and/or

repairing. You begin by gathering information from the most to the least important

sources.

Starting with the most important:

1. Your personal knowledge and experience with AC systems.

2. The vehicle operator's knowledge and experience—question him or her.

3. The work order.

4. Good test equipment and the HVAC system

The routine you follow when troubleshooting should proceed from the most to least

productive way of locating the problem and fixing the cause.

Troubleshooting & Service Procedures

Experienced troubleshooters talk to the operator if they can, then personally verify the

symptoms of the problem whenever possible. They attempt quick fixes on the basis

of their knowledge of common system problems and causes when appropriate. They

know where components are located, and make repairs when they have a good idea

of what the problem is. They fix the cause or causes as well as the problem. They are

confident of their knowledge and ability.

Note: The best troubleshooters all know who to call when they get

stuck. They know someone who knows more than they do and

are not too proud to ask for help or suggestions when needed. The

key—understanding system function

The Key-Understanding System Function

Your complete understanding of AC and heater systems and how they work, plus

what can go wrong, is the key to troubleshooting and repair. We have talked about

components and system function before. Now let’s take a little different approach in

describing what happens when the air conditioner is turned on. In Figure 8-1 we have

used numbers on the illustration to track normal air conditioner function.

Figure 8-1

An illustration of the typical

HVAC system. The numbers

follow the action when the

AC part of the system is

working properly (moving

heat out of the cab and into

the outside air).

Understanding System Function

When you turn on the air conditioner at the control panel (1), the thermostat (2), is

supposed to sense a warm temperature at the evaporator. A circuit in the thermostat

should close, allowing current to flow through the thermostat to the compressor clutch

field coil (3). When this happens, the clutch field coil becomes an electromagnet and

pulls the clutch drive plate (4) tight against the clutch pulley (5).

Note: The same AC switch (1) may also turn on the fan or blower motor

(2a) to circulate air in the cab. The air feels warm at first but will

cool quickly.

A belt connects the clutch pulley to a drive pulley (6) on the engine. The engine pro-

vides the power to turn the clutch pulley and drive the compressor (7) when the clutch

is engaged. When operating, the compressor compresses and pushes refrigerant gas

to the condenser (8), through the receiver-drier (9), and to the expansion valve (10)

orifice. When it does, it puts a lot of pressure on the gas. The compressor raises the

temperature and pressure of the refrigerant inside the high side of the system.

At the same time, the compressor is also sucking in low pressure refrigerant gas

from the expansion valve orifice, evaporator and through the low side of the system.

The movement of the refrigerant inside the system transfers heat energy from the cab

to the outside air for occupant comfort.

The automatic functions of the thermostat (or the pressure valve on some accumu-

lators), and the expansion valve, help maintain pressures and temperatures inside the

system at safe and efficient operating levels. Pressure and temperature are constantly

changing due to compressor and expansion valve action, the amount of heat energy

being moved and the environment or weather conditions.

The engine cooling system fan and clutch (11), and the evaporator blower motor

(2a), move a sufficient amount of air through the condenser and evaporator. On the

road, vehicle speed provides most of the (ram) air required for the condenser to work

right. In a parked or slow moving vehicle the engine fan (or roof or remote mounted

condenser and fans) moves sufficient air through the condenser fins.

Note: Clean refrigerant and refrigeration oil should be inside the system

in the amount specified by the manufacturer. Moisture, sludge

(moisture combined with refrigerant oil or desiccant), or desic-

cant particles will prevent the correct performance of the system

and may cause component damage.

A Troubleshooting Example

Remember the story at the beginning of this chapter? The vehicle operator pulled in

off the road and asked you to repair the rig. He was in such a hurry he didn’t tell you

anything except that the air conditioner wasn’t cooling. Here is the best way to handle

that kind of situation.

Troubleshooting & Service Procedures

Use your knowledge and experience. Ask yourself what could have caused a lack of

cooling in that rig! Did the compressor drive belt break? Did a pressure switch or

relief valve cutout the compressor because of high or low system pressure? Does the

switch or valve in this type of system reset itself? Could there be a superheat switch

and thermal limiter with a melted fuse. Did someone else service the system recently

and put in too much refrigerant?

Could there be contaminants in the system blocking the expansion valve (expan-

sion tube)? If there is a leak, why and how did refrigerant get out of the system? You

know if refrigerant can get out, air and moisture may get inside as well, especially if

the leak is on the suction side of the system. Could there be a restriction to refrigerant

flow in one of the high pressure lines because of a kink? From your knowledge and

experience, you already know about these possibilities and others when you talk to the

operator (before he has the chance to leave).

The right kind of questions can speed up troubleshooting and your service work

by pinpointing the problem(s) that needs fixing. Your conversation with the operator

might be as follows:

•

Answer: About an hour ago.

•

What steps did you take when you noticed the lack of cooling?

Answer: I put it on maximum cool.

•

Then what did you do?

Answer: When it wouldn’t cool, I opened the window and turned

the air conditioner off.

•

Is this problem new or has it happened before, and when?

Answer: In the last few days I’ve had problems with cooling off

and on—this is the first time it’s happened when I was close to a

place that did AC service.

•

Do you get any cooling at all?

Answer: Yes but it seems to quit after a while.

•

Do you still get air flow at the vents from the blower?

Answer: Yes.

•

When was your air conditioner checked thoroughly?

Answer: Before I bought the rig last May (a year ago).

•

Answer: Yes.

Takeuchi Hydraulic excavator TB1140 (Serial No. 514400002~). Operator's Manual - page 13