A/c-Heater System - Automatic Volvo 760 I

A/C SYSTEM SPECIFICATIONS

A/C SYSTEM SPECIFICATIONS

DESCRIPTION

Automatic Climate Control (ACC) system consists of several components which provide automatic control of vehicle interior temperature. System utilizes control panel, temperature sensors, blower motor, air mixing housing, vacuum controls, programmer and other components to accomplish automatic temperature control.

Scheme 1

Generally warm air flows from floor and defroster vents. Cold air flows from panel and steering column vents.

CONTROL PANEL

Control panel has a temperature selector dial and a mode selector lever.

Temperature Selector Dial

The temperature selector dial allows the user to select any temperature between 65-85°F (18-29°C). When set to the desired temperature, an electrical signal is sent to the programmer.

Mode Selector Lever

The mode selector lever sends vacuum signals to the programmer, which then decides if one or more functions should be activated. There are 7 positions for the mode selector lever.

"OFF"

A/C system is off, fan is on low speed and floor vents are open.

"ECON"

A/C system is off. All other operations controlled by programmer.

"LO"

A/C system is on, fan is on low speed. All other operations controlled by programmer.

A/C system is on. All other operations are controlled by programmer.

"HI"

A/C system is on, fan is on high speed. All other operations are controlled by programmer.

"B/L"

A/C system is on, air is directed to floor and panel louvers. All other operations are controlled by programmer.

"DEF"

A/C system is on, fan is on high speed. All air is directed to windshield.

Note. Except for the "DEF" position, the fan only operates when engine coolant is above 95°F (35°C), or the passenger compartment temperature is above 65°F (18°C).

Outer Sensor

This sensor determines temperature of incoming air and sends appropriate electrical signal to the programmer. Outer sensor is located in the fan housing.

Inner Sensor

This sensor measures the in-car temperature and sends appropriate electrical signals to programmer. Sensor is located on top of instrument panel behind dash.

AIR MIXING HOUSING

The air mixing housing operates by mixing cool and warm air to obtain the desired temperature. The advantage of this system is that temperature of interior can be changed quickly.

Vacuum Motors

A single vacuum motor controls the shutter for defroster and floor vents. Two vacuum motors control the shutters for the panel vents.

Recirculation of interior air is controlled by a vacuum motor. This occurs when mode selector dial is at maximum cooling position and interior temperature above 68°F (20°C). In this position a mixture of 85% passenger compartment air and 15% fresh air is circulated by system.

Heater Control Valve

Heater control valve is on inlet hose of the heater core. Vacuum signals from programmer and/or mode selector lever open or close this valve.

PROGRAMMER

The programmer (computer) is located below the glove box panel. It receives electrical signals from temperature sensors, temperature selector dial and vacuum signals from the mode selector lever. The programmer then controls fan speed, air mix shutters and water valve to maintain a desired temperature.

The programmer is located below the glove box panel. It consists of an amplifier, damper, transducer, rotary vacuum valve and vacuum motor.

AMPLIFIER

The amplifier receives electrical signals from temperature sensors, temperature selector dial and the damper. These signals are amplified and used to control the transducer.

DAMPER

This is a feedback potentiometer unit which senses position of the vacuum motor and compares it to signal of the amplifier. Strong signals from the amplifier are controlled by the damper. It is in series with amplifier so it can prevent vacuum motor suddenly going to full stop.

AIR INLET SHUTTER

1. Remove panel beneath glove box and glove box. (Scheme 3) Remove outer panel vents and air ducts.
2. With engine off, loosen adjusting screw. Make sure shutter is closed and vacuum motor is not activated. Retighten adjusting screw. Replace vent panels, air ducts and glove box components.

AIR MIX SHUTTER CONTROL ROD

1. Remove lower glove box panel and glove box. (Scheme 3) Remove outer panel vents and air ducts.
2. Start engine to provide vacuum. Set temperature selector dial to maximum heating position. Programmer control arm should move toward passenger compartment.
3. Pull control rod until end position is reached and secure to programmer arm. Cycle ACC system between maximum heating and maximum cooling to ensure proper function. Replace vent panels, air ducts and glove box components.

Scheme 2

TESTING

1. Check that during ACC operations, A/C compressor is engaged in all positions except in "OFF" and "ECON" positions. A click from compressor clutch will be the only noise heard.
2. The compressor will not turn on when outside temperature is below 50°F (10°C).

Note. The compressor operation has a 10 second delay until after alternator begins charging.

FUNCTION CHECK

1. Set mode selector lever to "AUTO" position. Start engine and run until electric cooling fan starts. Turn temperature selector dial to maximum heating.
2. Check that fan operates at highest speed. About 80% warm air should come from floor vents and 20% from defroster vents.
3. Set temperature selector dial to obtain maximum cooling. Fan should drop to low speed after 2-10 seconds and then increase to high speed again. Cold air should come from panel vents only.
4. Set temperature selector to 75°F (24°C). Check operations for about 1.5 minutes. Fan speed should be low, and air distribution and temperature should stabilize.
5. Set mode selector lever to "LO" position. Check that fan operates at lowest speed.
6. Set mode selector lever to "HI" position. Check that fan operates at highest speed.
7. Set mode selector lever to "ECON" position. ACC system should function same as if in "AUTO" position except that A/C compressor will not engage.
8. Set mode selector lever to "B/L" position. Cool air should come from panel vents. Warm air should also come from floor and defroster vents. Fan speed is regulated automatically.
9. Set mode selector lever to "DEF" position. Check that fan operates at highest speed. About 80% of air should come from defroster vents. About 20% of air should come from floor ducts.

Scheme 3

VACUUM CHECK

1. ACC system requires a minimum of 10 in. Hg vacuum to operate correctly. Check for vacuum at Violet vacuum hose connector at rear of engine compartment.
2. Remove glove box panel and glove box. (Scheme 3) Check for vacuum at Violet hose on programmer. Check all other vacuum hoses and connections. (Scheme 4) Replace components removed.

Scheme 4

ACC Compressor Delay Relay

Using a voltmeter, check for voltage at terminal No. 87. Connect a power supply to terminals No. 61 and No. 15. Ground terminal No. 85. Check for voltage at terminal No. 87 after 10 seconds. If no voltage is present, replace relay.

ACC Fan Relay

Using a voltmeter. Check for voltage at terminal No. 2. Connect a power supply to terminals No. 4 and No. 1. Ground terminal No. 3. Check for voltage at terminal 2. If no voltage is present, replace relay.

Temperature Sensors

1. Using an ohmmeter, check temperature sensor in control panel for continuity above 65°F (18°C) only. Cool sensor below 65°F (18°C) and check that no continuity is present. If sensor test is not good, replace sensor.
2. Check thermal switch on coolant hose for continuity between 86-104°F (30-40°C). Cool thermal switch. Continuity should be lost before temperature goes below 50°F (10°C). Replace switch if it does not test correctly. NOTE: The outer sensor resistance value can be checked from air intake. Remove windshield wipers, upper cowl support and cover from air intake. If replacement is necessary, See procedure in REMOVAL & INSTALLATION section of this article.
3. Check that outer sensor resistance is 30-40 ohms at 68-86°F (21-30°C). If resistance is 65-100 ohms, replace sensor. Higher air temperatures corresponds to a lower sensor resistance.

Trouble Shooting. Scheme 5

Removal

Disconnect battery lead. Discharge refrigerant from system using approved refrigerant recovery/recycling equipment. Remove electrical connectors and pressure hoses from compressor (plug open hoses). Loosen mounting bolts. Remove drive belt and bolts. Lift compressor from vehicle.

Installation

To install, reverse removal procedure. Tighten belt to specification. Refill system and check for leaks.

Disconnect battery lead. Discharge refrigerant from system using approved refrigerant recovery/recycling equipment. Remove grille and air guide at spoiler. Detach cross brace in front of condenser from upper support panel. Remove refrigerant hoses from condenser (plug open hoses). Remove condenser.

To install, reverse removal procedure. Use new "O" rings coated with oil. Refill system and check for leaks.

Removal & Installation

Remove panel surrounding control panel. Remove control panel screws and pull panel out. To install, reverse removal procedure.

1. Discharge refrigerant from system (plug open hoses) using approved refrigerant recovery/recycling equipment. Disconnect evaporator connectors in engine compartment. Remove panel beneath glove box and glove box. (Scheme 3) Disconnect all electrical wires. Remove screws from lower fan housing. NOTE: Two screws are hidden behind fan and evaporator housing.
2. Withdraw lower fan housing cover and lift out evaporator.

Clean sealer from lower fan housing. Transfer filter and rubber seal to new evaporator if being replaced. Apply sealer to lower fan housing. Install evaporator in housing. Reverse removal procedure to complete remaining installation. Refill system and check for leaks.

1. Remove panel beneath glove box. (Scheme 3) Remove mounting screws and lower motor out of housing.
2. Disconnect wiring and remove hose for air cooling. Remove motor with fan.

To install, reverse removal procedure.

1. Disconnect battery lead. Pinch hoses to heater core from engine compartment and disconnect.
2. Remove ashtray. Pull out center storage compartment in dash. Remove 2 screws behind plastic cover.
3. Remove panel around gear shifter and parking brake. Disconnect electrical plug. Remove 2 screws from bottom of storage compartment between seats. Remove center package tray on top of drive shaft hump.
4. Remove panel and air duct below left dash. Pull floor mat down from center side panel. Remove left side panel screws.
5. Remove panel beneath glove box and glove box. (Scheme 3) Remove lighting. Pull floor mat down from center side panel. Remove left side panel screws.
6. Remove radio and radio compartment. Remove screws holding side panels to center dash brackets. Remove side panels.
7. Remove panel around control panel. Remove radio compartment console. Loosen screws holding control panel. Disconnect vacuum hoses and electrical plug to control panel and remove control panel.
8. Remove all vent ducts attached to distribution unit and center panel vent. Remove vacuum hoses to vacuum motors and aspirator. Remove distribution unit from vehicle.
9. Remove straps holding heater core to housing. Lift heater core from vehicle.
10. Remove panel from distribution unit. Replace vacuum motors as required.

To install, reverse removal procedure. Reconnect vacuum motor hoses as follows: Red to upper shutter for panel vents, Blue to defroster vents and Light Brown to lower shutter for panel vents.

Remove panel beneath glove box and glove box. (Scheme 3) Disconnect air hose from sensor. Remove wiring and clip. Lift out sensor.

Position sensor and secure with clip. Reverse removal procedure to complete remaining installation.

Remove panel beneath glove box and glove box. (Scheme 3) Disconnect air hose from sensor. Remove wiring and clip. Lift out sensor.

1. Sensor is located in fan housing. To replace, remove panel beneath glove box and glove box. (Scheme 3) Remove outer panel vents and air ducts.
2. Disconnect air inlet shutter control rod from vacuum motor. Remove vacuum motor mounting screws and let hang loose. Disconnect sensor wire connector. Remove mounting screws and sensor.

Replace sensor with mounting screws. Plug wire connector on sensor. Reinstall vacuum motor and air inlet shutter control rod. Adjust control rod. See ADJUSTMENTS in this article. Reverse removal procedure to complete remaining installation.

1. Remove panel beneath glove box and glove box. (Scheme 3) Remove outer panel vents and air ducts. Disconnect control rod from air mix shutter. Disconnect electrical plug on left side of programmer.
2. Remove securing clips for vacuum hoses and remove vacuum connector. Remove programmer mounting screws and remove programmer from housing.

To install, reverse removal procedure. Air mix control rod must be readjusted. See procedures in ADJUSTMENTS in this article.

Disconnect battery lead. Discharge refrigerant from system using approved refrigerant recovery/recycling equipment. Detach hoses from receiver-drier (plug open hoses). Disconnect electrical connector. Remove from mounting bracket.

Transfer pressure sensor to new receiver-drier if necessary. To install, reverse removal procedure.

1. To remove the air inlet shutter vacuum motor, remove panel beneath glove box and glove box. (Scheme 3) Remove outer panel vents and air ducts. Disconnect vacuum hose and control rod from vacuum motor.
2. To remove the panel vent or defroster vent motors remove heater core distribution unit.

To install, reverse removal procedure. Install air inlet vacuum motor. Reconnect vacuum hose, mount in place and adjust. See procedures in ADJUSTMENTS in this article.

Automatic A/C-Heater Systems Wiring Diagram. Scheme 6

See also:
• ADJUSTMENTS