The heater system uses a two-way-flow full-air-mix
system that features high performance and low
operating noise. It includes an independent face air
blowing function. In addition, an air purifier which
carries out fine A/C control has been included.

SAFETY PRECAUTIONS

WARNING

Wear safety goggles and gloves when
servicing the refrigeration system to prevent
severe damage to eyes and hands.

Because R-134a refrigerant is a hydro fluorocarbon
(HFC) which contains hydrogen atoms in place of
chlorine atoms, it will not cause damage to the ozone
layer.
Ozone filters out harmful radiation from the sun. To
assist in protecting the ozone layer, Mitsubishi
Motors Corporation recommends an R-134a
refrigerant recycling device.
Refrigerant R-134a is transparent and colorless in
both the liquid and vapor state. Since it has a boiling
point of

−

29.8

C (

−

21.64

F) at atmospheric pressure,

it will be a vapor at all normal temperatures and
pressures. The vapor is heavier than air, non-
flammable, and non-explosive. The following
precautions must be observed when handling R-
134a.

WARNING

Do not heat R-134a above 40

°°°°

C (104.0

°°°°

F) or it

may catch fire and explode.

R-134a evaporates so rapidly at normal atmospheric
pressures and temperatures that it tends to freeze
anything it contacts. For this reason, extreme care
must be taken to prevent any liquid refrigerant from
contacting the skin and especially the eyes. Always
wear safety goggles when servicing the refrigeration
part of the A/C system. Keep a bottle of sterile
mineral oil handy when working on the refrigeration
system.

1. Should any liquid refrigerant get into the eyes, use

a few drops of mineral oil to wash them out. R-
134a is rapidly absorbed by the oil.

2. Next splash the eyes with plenty of cold water.

3. Call your doctor immediately even though

irritation has ceased after treatment.

CAUTION

Keep R-134a containers upright when charging
the system.
In most instances, moderate heat is required to bring
the pressure of the refrigerant in its container above
the pressure of the system when charging or adding
refrigerant.
A bucket or large pan of hot water not over 40

(104.0

F) is all the heat required for this purpose. Do

not heat the refrigerant container with a blow torch or
any other means that would raise temperature and
pressure above this temperature. Do not weld or
steam clean on or near the system components or
refrigerant lines.

WARNING

The leak detector for R-134a should be used
to check for refrigerant gas leaks.

CAUTION

Do not allow liquid refrigerant to touch bright
metal or it will be stained.
When metering R-134a into the refrigeration system
keep the supply tank or cans in an upright position. If
the refrigerant container is on its side or upside
down, liquid refrigerant will enter the system and
damage the compressor.
Refrigerant will tarnish bright metal and chrome
surfaces, and in combination with moisture can
severely corrode all metal surfaces.

Items

Specifications

Heater unit

Type

Two-way-flow full-air-mix system

Heater control assembly

Dial type

Compressor

Model

Scroll type <MSC90C>

Dual pressure
switch kPa (psi)

High-pressure switch

→

OFF: 2,942 (426.7), OFF

→

ON: 2,354 (341.4)

Low-pressure switch

→

OFF: 196 (28.4), OFF

→

ON: 221 (32.1)

Refrigerant and quantity g (oz)

R-134a (HFC-134a), Approximately 630

−

670 (22.2

−

23.6)

MANUAL A/C DIAGNOSIS

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HEATING AND AIR CONDITIONING

55-4

OPERATION

Condenser fan and radiator fan control

•

For the operation of each fan, refer to GROUP
14, Diagnosis - Symptom Chart

P.14-2

Compressor control

When operating the air conditioning switch

•

The air thermo sensor, which senses the
temperature of the air flowing out of the
evaporator, deactivates the compressor at 5

(41.0

)

or below.

•

The dual pressure switch turns OFF when the
refrigerant pressure becomes excessively high or
low, thus protecting the compressor circuit. (See
Table below.)

•

When the air thermo sensor is activated, the dual
pressure switch is ON, and the ignition switch,
blower switch, and air conditioning switch are
ON, the A/C compressor relay is energized.

When operating the air outlet changeover control

knob

•

When the air outlet changeover control knob is
moved to DEFROSTER or DEFROSTER/FOOT
position, the defroster switch, which is connected
in series to the air conditioning switch, is turned
on. The other compressor control than the above
is the same as that when operating the air
conditioning switch.

When compressor locks <vehicles with 3.0 L

engine>

•

Since the compressor and alternator are driven
by the same belt, the electric generating function
of the alternator also stops when the belt is
broken. In order to assure the electric generating
function of the alternator, there is an A/C-ECU to
prevent breaking of the belt due to slipping when
the compressor locks. The A/C-ECU makes a
comparative calculation of the compressor
revolutions and the engine revolutions which are
detected by the revolution pick-up sensor. When
70% or more slip ratio continues for 3 seconds or
more, the A/C compressor relay goes from on to
off; at the same time, the operation display in the
air conditioner switch blinks to announce an
abnormality.

A/C Compressor Relay ON Conditions

M A N U A L A /C D IA G N O S IS

INTRODUCTION TO HEATER, AIR CONDITIONING AND VENTILATION DIAGNOSIS

M1552012200098

With this system, after the outside air or inside air is
taken in through the damper, it is fed to the
evaporator by the blower fan and motor and cooled.
The air cooled by the air mix damper is mixed
appropriately with the warmed air to achieve a
comfortable temperature. If the A/C does not operate
or the cooled air is not discharged, the machine

components or relay may be faulty.

Ignition switch (IG2)

NOTE: . A/C compressor relay is de-
energized when any one switch, sensor or
control unit shown on the left turns off.

NOTE: . The

marked device measures the

temperature of the outlet air, and according
to the control characteristics of the magnetic
clutch for the compressor, the automatic
compressor controller outputs the "HI" signal
(12V). When air of 5

C (41.0

F) or less

blows out of the evaporator, the compressor
magnetic clutch will be turned off.

Blower switch

Air conditioning switch or defroster switch

Air thermo sensor

Dual pressure
switch

Low-pressure side 221 kPa
(32.1 psi) or higher

High-pressure side 2,942 kPa
(426.7 psi) or below

A/C compressor relay driving transistor (within
automatic compressor controller and engine control
module <M/T>, powertrain control module <A/T>)

MANUAL A/C DIAGNOSIS

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HEATING AND AIR CONDITIONING

55-5

HEATER, AIR CONDITIONING AND VENTILATION DIAGNOSTIC TROUBLESHOOTING
STRATEGY

M1552009600096

Use these steps to plan your diagnostic strategy. If
you follow them carefully, you will be sure that you
have exhausted most of the possible ways to find a
heater, air conditioning and ventilation fault.
1. Gather information from the customer.

2. Verify that the condition described by the

customer exists.

3. Find the malfunction by following the Symptom

Chart.

4. Verify malfunction is eliminated.

SYMPTOM CHART

M1552009900086

NOTE: For symptoms marked with an asterisk the
condenser fan might not operate when there is an air
conditioning low load from the air conditioning
condenser control, so remove the battery terminal (-)
and then check the symptoms after 5 minutes since
initial start control after reconnection.

SYMPTOM PROCEDURES

INSPECTION PROCEDURE 1: WHEN THE IGNITION SWITCH IS "ON," THE A/C DOES NOT OPERATE.

DIAGNOSIS

STEP 1. Check for refrigerant leaks.

Q: Is the refrigerant leaking?

YES : Repair the leak. Then go to Step 11.
NO : Go to Step 2.

STEP 2. Check for excessive refrigerant.

Q: Is the refrigerant in good condition?

YES : Go to Step 3.
NO : Use the refrigerant recovery station to remove all of

the refrigerant, and then calculate the amount of the
refrigerant and charge it. Then go to Step 11.

SYMPTOMS

INSPECTION
PROCEDURE

REFERENCE
PAGE

When the ignition switch is "ON," the A/C does not operate.

P.55-5

When the air outlet changeover control knob is moved to DEFROSTER or
DEFROSTER/FOOT position, the A/C or the inside/outside air
changeover damper motor does not operate.

P.55-9

When the A/C is operating, temperature inside the passenger
compartment does not decrease (cool air is not emitted).

P.55-9

Blower fan and motor does not turn.

P.55-11

Blower fan and motor does not stop turning.

P.55-13

When the A/C is operating condenser fan or radiator fan does not turn.*

P.55-15

The A/C indicator flashes <Vehicles with 3.0l engine>

P.55-15

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