Automatic Climate Control Unit - Function Check (GROUP 87, NO. 101) — 1983 Volvo 760 Base Service Manual ~ FixVault

SERVICE INFORMATION

This bulletin applies to the U.S. and Canadian markets.

This bulletin contains a simplified version of the function check. Vacuum chart, vacuum schematic, wiring diagram and more detailed fault tracing chart are also included to simplify diagnosis.

AIR DISTRIBUTION ACC

Generally speaking in all the programmed positions, warm air flows from the floor and defroster vents whereas cold air flows out of the panel vents and the steering column vent. See Fig 1 .

Fig 1: Air Distribution from Vents

FUNCTION CHECK

NOTE:

the fan starts only if passenger compartment temperature is above 18°C (64°F) or if coolant temperature is above approx. 35°C (95°F).
compressor is engaged/disengaged automatically.
that compressor is not engaged until 10 seconds after the alternator has begun to charge.

Check during operation that:

compressor is engaged (i.e. cool air supply) in all positions except OFF and ECON. A "click" is heard when compressor engages/disengages, no other noise should be heard. Lowest ambient temperature at which compressor engages is approx. 10°C (50°F).
fan operates quietly.

Set mode selector lever to AUTO. Start engine and leave running until fan starts. Turn temperature selector to max heat.
Check: That fan operates at highest speed. Approx. 80 percent of warm air should come from floor ducts and approx. 20 percent from defroster vents.
Turn temperature selector to lowest temperature. Fan should drop to low speed after 2-10 seconds and then increase immediately to high speed again. The cold air should only be emitted from the panel vents.
Set temperature selector to normal temperature (Approx. 75°F = 24°C). Check fan speed and air distribution for approx. 1.5 minutes. Fan speed should be relatively low and air distribution stable.
NOTE: Temperature must not fluctuate.

Air distribution is dependent on:
- ambient air temperature
- passenger compartment temperature
- temperature setting
Set mode selector lever to ECON. Climate unit should function in the same manner as when set to AUTO even though compressor is disengaged (i.e. no cold air is emitted from vents).
Set mode selector lever to LO. Check that fan operates at lowest speed.
Set mode selector lever to HI. Check that fan operates at highest speed.
Set mode selector lever to B/L. Fan speed is regulated automatically. Check that air is emitted from panel and floor vents. Some air should come from the defroster vent. Air from floor ducts should be warmer than air from panel vents.
Set mode selector lever to DEF. Fan speed should increase to max. Approx. 80 percent of air should be emitted from defroster vents and approx. 20 percent from floor ducts.
Set mode selector lever to OFF. Fan speed should drop to-lowest. Most of the air should come from floor ducts. Some air from defroster.

Fig 2 shows the mode of operation in each set position (read from the top to bottom).

Fig 2: Operation Diagram

VACUUM DIAGRAM

Fig 3 shows the different colors of the vacuum hoses and how they are connected.

Fig 3: Vacuum Hose Schematic

FAULT TRACING, ACC

When carrying out the following checks, make sure that the battery is fully charged and that there is sufficient vacuum in the system. The vacuum should be 35 kPa (10 inch hg).

The vacuum in the system can be checked by measuring the time it takes for the shutter to move between the end positions.

Temperature approx. 20-25°C (68-77°F).

Time check from cold to warm

----------------

Room temp. approx. 20-25°C (68-77°F)

Set the mode selector to "auto".
Move the temperature lever from max cold to max warm 65-85°F. Time taken for warm air to be emitted: approx. 10 seconds.

Move the temperature lever from max warm to max cold. Time taken: with air recirculation [above 20°C (68°F) in room temp.] approx. 25 seconds. Time taken: without air recirculation [above 20°C (68°F) in room temp.] approx. 16 seconds.

APPROXIMATE TIME FOR VACUUM CONTROL (ROOM TEMP. APPROX. 20 - 25° C)

Temperature lever	Mode selector moved from	Air from	Approx. time taden (secs.)
Max. cool (65° F)	OFF-> ECON	Panel vent	10-12
Max. cool (65° F)	OFF -> B/L	Floor & panel vents	5-8
Max. cool (65° F)	OFF -> DEF	Defroster vents	3-6
Max. cool (65° F)	OFF -> auto (without air recir)	Panel vents	15-20
Max. cool (65 °F)	OFF -> auto (w air recirc above 20° C room temp)	Panel vents	15-20

If vacuum appears to be insufficient check the following: * That vacuum connection (violet hose) at rear of engine compartment is correctly connected and does not leak.
Remove glove compartment. Note covers over screws in glove compartment and cap over clip to right of switch. See Fig 4 . Check for vacuum at programmer. Thick violet line is vacuum inlet. Disconnect vacuum line and test with finger.

Fig 4: Removal of Glove Compartment

FAULT TRACING

NOTE: Faults are not in order of probability.

FAULT TRACING

Symptom	Probable Cause	Remedy
Does not operate as expected Irregular operation of ACC	Vacuum connection leaking at programmer or control panel	Check connectors. Remove glove compartment, control panel.
Does not operate as expected Irregular operation of ACC	Poor electrical contact of 6-pole gray connectors or programmer connectors.	Remove glove compartment. Check connectors.
Does not operate as expected Irregular operation of ACC	Internal programmer fault.	Replace programmer.
Insufficient air from panel vents. Warm air bleeds from panel vents when max heat is selected (temperature selector dial moved to max limit of warm range travel)	Panel shutters do not close fully or jams in some positions. Operating arm for lower shutter incorrectly shaped.	Check/ re-shape operating arm.
Insufficient air supplied to floor at full heat - too much Rattling or noisy operation	Mounting bracket for defroster shutter loose	Check. Disconnect blue hose & check vacuum. If incorrect, replace distribution (center) housing.
Air from incorrect vent	Vacuum hose incorrectly connected	Check. Remove panel beneath steering column.
Air regulation very slow or does not function	Vacuum hoses kinked or obstructed at programmer or control panel	Check hoses. Remove panel beneath steering panel and glove compartment. Remove control panel
Vibration from fan	Fan out of balance	Replace fan.

NOTE: ACC must be set to Auto when carrying out following fault tracing procedures:

FAULT TRACING (2 of 2)

Symptom	Probable Cause	Remedy
Max heat, max fan speed	One of sensors disconnected or defective (Infinite resistance). Input leads to programmer from sensors disconnected.	Check sensors.
Max cool, max fan speed	One of sensors short-circuited (low resistance)	Check sensors.
Max heat all the time even through panel vents. Fan speed OK.	Air-mix shutter lumped out of position	Check air-mix shutter.
Max heat all the time even through panel vents. Fan speed OK.	Internal programmer fault	Replace programmer
When starting from cold fan operates only in DEF until complete passenger compartment (above 18 C = 65 F).	Thermal switch on heater core output hose does not complete circuit for fan motor.	Check thermal switch in engine compartment.
Fan only operates when coolant temp above 35 C (95 F).	Temp. sensor on control does not complete current circuit. (Should round at approx. 18 C = 65 F)	Check temperature sensor.
No fan delay. (Cold air blown in during cold weather)	Continuous current flow through: 1. Thermal switch in engine compartment 2. Temperature sensor in control panel.	Check thermal switch and temp sensor.
Fan does not operate despite correct temp sensor and thermal contact	Fan relay defect.	Check fan relay.
Fan speed does not alter	No vacuum in the unit.	Check vacuum.
Fan speed does not alter	No voltage across programmer.	Check positive supply (input lead) to programmer
-constant low fan speed -water valve open despite full cold setting -no recirculation -too warm in car in relation to temp setting. Programmer function in Auto	-defect out temp sensor loose resistor	Check outer temp. Measure resistance

Automatic Climate Control Unit - Function Check (GROUP 87, NO. 101)