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Volvo 850. Manual - part 59

temperature control dial, and engine coolant temperature.

At low outside temperatures, the ECC control module selects

floor/defrost setting, with a slight amount of bi-level air if

sunshine is present. If outside temperature is between 50-66

F (10-

C), a varying degree of bi-level air is selected. At temperatures

greater than 68

F (20

C), all air is directed to instrument panel

vents.

The ventilation air distribution setting is selected if

driver’s side control panel is set for maximum cooling. The

floor/defrost setting is selected if maximum heating is selected.

The defrost air distribution setting is selected if engine is

cold and outside and interior temperatures are also low. This changes

to varying degrees of floor/defrost air distribution as engine coolant

temperature increases. The transition from defroster to

floor/defroster setting takes place more quickly in sunshine.

AIR TEMPERATURE SENSORS & SOLAR SENSOR

Two interior temperature sensors and 2 duct temperature

sensors are required for individual temperature control of driver’s

and passenger’s sides. Each interior temperature sensor incorporates a

fan which draws air through sensor.

The resistance of the air temperature sensors decreases as

temperature increases. The solar sensor, combined with the theft alarm

diode, is a photodiode which generates a current when exposed to solar

radiation.

DAMPER MOTORS

The temperature control damper motors, recirculation damper

motor, floor/defroster damper motor, and ventilation damper motor are

all identical, but their control range varies according to the damper

being controlled.

The damper motors have a position sensor to enable the ECC

control module to determine damper position, learn the damper limit

positions, and to detect any fault in damper motor. The ventilation

damper is operated by damper motor through 2 gear segments; one fitted

to damper motor shaft and the other on ventilation damper shaft.

FAN CONTROL

Heater (blower motor) fan speed is variably controlled by ECC

output (power) stage in response to signals from ECC control module.

The ECC control module digital control signals vary in length

according to required fan speed.

The ECC output stage has an electronic unit which receives

the digital control signals and converts them to voltage. If there is

no control signal or the fan is disabled, the ECC output stage sends a

diagnostic signal to inform the ECC control module of the fault.

If fan speed control lever is set to AUT (automatic) mode,

fan speed is influenced by the position of driver’s side temperature

control dial, driver’s side interior temperature sensor, vehicle

speed, and engine coolant temperature.

The highest fan speed is selected if driver’s side

temperature control dial is set to maximum or minimum cooling or

heating. The greater the difference between the desired and actual

temperatures, as sensed by the driver’s side temperature sensor, the

higher the fan speed.

As vehicle speed increases, the fan speed will be reduced to

maintain a constant airflow throughout the passenger compartment. When

heating the passenger compartment after starting a cold engine, the

fan speed is gradually increased as engine coolant temperature rises.

RECIRCULATED AIR MODE

The ECC control module selects recirculated air mode only for

a combination of cooling and high outside temperature, provided that:

* There is a considerable difference between the desired and

actual temperature on driver’s side. The quantity of

recirculated air will vary between 70-100 percent, depending

on difference in temperature.

* A high fan speed is manually selected. In this case, the

recirculation damper will be set to a mid-position (50

percent of the air will be recirculated).

Recirculation Motor

This motor operates the recirculation damper by means of a

mechanical linkage in response to signals from ECC control module.

Recirculation Switch

The off position of REC (recirculation) switch corresponds to

automatic operation, the ECC control module determines whether

recirculation is required.

Air Distribution Switch

With air distribution switch in defroster position,

recirculated air mode always cuts out, as humidity in passenger

compartment will normally be higher than that of outside air.

Recirculation Damper

In AUT (automatic) mode, recirculation damper movement is

limited to fractions of a second. It takes about half a minute from

full recirculation to take effect if outside temperature is high.

TEMPERATURE CONTROL

Individual temperature control is provided by the driver’s

and passenger’s side temperature control damper motors in response to

signals from ECC control module.

The ECC control module computes temperature control damper

motors based on inputs from temperature dial settings, duct

temperature sensors, interior temperature sensors, solar sensor,

engine coolant temperature sensor, and outside (ambient) temperature

sensor.

The air temperature is monitored downstream of temperature

control dampers by the duct temperature sensors. The difference

between the desired and actual interior temperature, as monitored by

interior temperature sensors, has a direct effect on temperature

control damper positions.

In direct sunlight, the temperature control dampers are

positioned to provide a lower temperature, as determined by solar

sensor input. If the engine is cold and outside temperature is low,

the temperature control dampers are set for more heat to reach the

desired temperature faster.

TROUBLE SHOOTING

SELF-DIAGNOSTICS

The Electronic Climate Control (ECC) control module can

detect faults in the system and store Diagnostic Trouble Codes (DTCs).

If a fault is present, system informs driver by flashing AC OFF and

REC switch LEDs for 20 seconds.

A fault warning is given when a fault is discovered or

present each time ignition is turned on or engine started. DTCs will

remain stored until cleared by an input code.

NOTE: Test Unit (981 3190) and Adapter (981 3194) are required for

DTC diagnosis. The Volvo Diagnostic Key (998 8670) may be

used to perform self-diagnostics. Follow tool manufacturer’s

instructions.

There are 3 different test modes/settings which can be

selected for reading off DTCs. TEST MODE 1 may be used for reading off

DTCs detected by control unit (up to 47 codes can be stored). TEST

MODE 2 checks signals from speedometer and solar sensor.

TEST MODE 4 is used to check electrical circuits in A/C

system, reset information on damper motor limit positions and change

data transmission speed from ECC control module to on-board diagnostic

unit.

NOTE: Ignition must be turned off before switching from one test

mode to another.

ENTERING SELF-DIAGNOSTICS

1) Connect selector cable from diagnostic unit "A" to

terminal No. 1 of diagnostic unit "B", located behind right headlight.

See Fig. 2.

2) Turn ignition on. LED on diagnostic unit "A" should start

flashing. Each DTC (3-digits) consists of a series of flashes with a

short break between each series. DTCs are displayed in ascending

order. See AUTOMATIC A/C-HEATER SYSTEM DIAGNOSTIC TROUBLE CODES table.

Fig. 2: Identifying Diagnostic Units

Courtesy of Volvo Cars of North America.

AUTOMATIC A/C-HEATER SYSTEM DIAGNOSTIC TROUBLE CODES

Code # Condition/Affected Circuit

1-1-1 ..................... No Fault Found By Diagnostic System

1-2-1 .......... Outside Temp. Sensor Circuit Shorted To Ground

1-2-2 .................................... Outside Temp. Sensor

Circuit Open Or Shorted To Power

1-2-3 .... Driver’s Side Temp. Sensor Circuit Shorted To Ground

1-2-4 .............................. Driver’s Side Temp. Sensor

Circuit Open Or Shorted To Power

1-2-5 ....... Pass. Side Temp. Sensor Circuit Shorted To Ground

1-2-6 ................................. Pass. Side Temp. Sensor

Circuit Open Or Shorted To Power

1-3-1 ....... Driver’s Side Duct Temp. Sensor Shorted To Ground

1-3-2 ......................... Driver’s Side Duct Temp. Sensor

Circuit Open Or Shorted To Power

1-3-3 .......... Pass. Side Duct Temp. Sensor Shorted To Ground

1-3-4 ............................ Pass. Side Duct Temp. Sensor

Circuit Open Or Shorted To Power

1-3-5 ........................ No Engine Temp. Frequency Signal

1-4-1 ........ Driver’s Side Temp. Switch Faulty Control Signal

1-4-3 ........... Pass. Side Temp. Switch Faulty Control Signal

1-4-5 ........... Air Distribution Switch Faulty Control Signal

1-5-1 ..... Fan Speed Sensor Control Signal Missing Or Too High

1-5-2 ....... Fan Speed Sensor Control Signal Shorted to Ground

2-1-1 .............. Driver’s Side Damper Motor Position Sensor

Circuit Open Or Shorted To Power

2-1-2 .............. Driver’s Side Damper Motor Position Sensor

Shorted To Ground

2-2-1 ................. Pass. Side Damper Motor Position Sensor

Circuit Open Or Shorted To Power

2-2-2 ................. Pass. Side Damper Motor Position Sensor

Shorted To Ground

2-3-1 ................ Ventilation Damper Motor Position Sensor

Circuit Open Or Shorted To Power

2-3-2 ................ Ventilation Damper Motor Position Sensor

Shorted To Ground

2-3-3 .............. Floor/Defrost Damper Motor Position Sensor

Circuit Open Or Short To Power

2-3-4 .............. Floor/Defrost Damper Motor Position Sensor

Shorted To Ground

2-3-5 .............. Recirculation Damper Motor Position Sensor

Circuit Open Or Short To Power

2-3-6 ..................... Recirculation Damper Motor Position

Sensor Shorted To Ground

3-1-1 ... Driver’s Side Damper Motor Shorted To Ground Or Power

3-1-2 ...... Pass. Side Damper Motor Shorted To Ground Or Power

3-1-3 ..... Ventilation Damper Motor Shorted To Ground Or Power

3-1-4 ... Floor/Defrost Damper Motor Shorted To Ground Or Power

3-1-5 ... Recirculation Damper Motor Shorted To Ground Or Power

3-2-1 .............. Driver’s Side Damper Motor Active Too Long

3-2-2 ................. Pass. Side Damper Motor Active Too Long

3-2-3 ................ Ventilation Damper Motor Active Too Long

3-2-4 .............. Floor/Defrost Damper Motor Active Too Long

3-2-5 .............. Recirculation Damper Motor Active Too Long

4-1-1 ......... Pass. Compartment Fan Overcurrent Or Seized Fan

4-1-2 .............................. Driver’s Side Temp. Sensor

Intake Fan Shorted To Ground

4-1-3 .............................. Driver’s Side Temp. Sensor

Intake Fan, No Control Voltage

4-1-4 ............ Driver’s Side Temp. Sensor Intake Fan Seized

4-1-5 .... Pass. Side Temp. Sensor Intake Fan Shorted To Ground

4-1-6 .. Pass. Side Temp. Sensor Intake Fan, No Control Voltage

4-1-7 ............... Pass. Side Temp. Sensor Intake Fan Seized

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