A/C SYSTEM SPECIFICATIONS
| Application | Specification | |
|---|---|---|
| Compressor Type | Nippondenso 10-Cyl. | |
| Compressor Oil Capacity | 2.7 oz. | |
| Compressor Belt Tension | ||
| New | 100 lbs. | |
| Used | 80-90 lbs. | |
| Refrigerant (R-12) Capacity (1) | 37 oz. | |
| System Operating Pressures (2) | ||
| High | 154-255 psi (11-18 kg/cm 2 ) | |
| Low | 19-46 psi (1.3-3.2 kg/cm 2 ) | |
| (1) When recharging system, add at least 18 oz. of refrigerant to low side port BEFORE operating compressor. (2) Measure operating pressures with temperature at 77°F (25°C). | ||
| (1) | When recharging system, add at least 18 oz. of refrigerant to low side port BEFORE operating compressor. |
| (2) | Measure operating pressures with temperature at 77°F (25°C). |
A/C SYSTEM SPECIFICATIONS
DESCRIPTION
| CAUTION | When discharging air conditioning system, use only approved refrigerant recovery/recycling equipment. Make every attempt to avoid discharging refrigerant into the atmosphere. To avoid accidental air bag deployment, see AIR BAG DEACTIVATION SERVICING PRECAUTIONS in this article. |
The A/C-heater control panel has buttons to control system. Blower speed is controlled automatically according to difference between selected temperature and interior temperature. Blower speed can also be controlled manually. Depressing the HI or LO buttons will raise or lower blower speed. The WARMER or COOLER buttons are used to raise or lower temperature as desired.
The digital climate control system automatically maintains temperatures set between 64°F (18°C) and 85°F (29°C). If a temperature above 85°F (29°C) is selected, the word HI appears in temperature display. If a temperature below 64°F (18°C) is selected, the word LO is displayed. Selection of these temperatures overrides automatic climate control system.
A/C SYSTEM
If the vehicle interior is hot and the climate control system is programmed to maintain a temperature of 75°F (24°C), the system will operate as follows. Recirculation doors will open. Fresh air door will close and 85% of inside air will be recirculated. Heater control valve will close and air will flow from registers. Temperature control door should be closed. No air should flow through heater core. Blower speed will increase from low to high over a 10-second period. As interior cools down, recirculation door will close as fresh air door begins to open.
If needed, heater control valve will open; temperature control door will begin to open and blower speed will slow down. Air flowing from registers will warm slightly. There are 3 factors controlling operation of system: outside temperature, inside temperature and temperature setting.
If vehicle is very cold and climate control system is programmed to maintain a temperature of 75°F (24°C), the system will operate as follows. Recirculation door will close, and outside air will flow into system. Heater control valve will open, allowing coolant to flow through heater core. Air will flow from floor vents. Temperature control door will open, and all air will flow through heater core. Blower speed can be controlled manually, regardless of heater setting, by pushing HI or LO button.
Note. The blower delay feature is overridden when the DEFROST button is depressed. Hot air does not flow from registers in DEFROST mode. If system is in BI-LEV (bi-level) mode, warm air flows out floor vents and cooler air flows out registers.
A/C-HEATER CONTROL PANEL & AIR DISTRIBUTION
The A/C-heater control panel receives input from driver and system components. It processes input signals and operates system accordingly. (Scheme 1)
OFF Mode
When the OFF button is pressed, the system is switched off. (Scheme 1) Fresh air intake is closed and temperature display is turned off. Outside temperature is shown on display.
Note. If vacuum system fails, climate control automatically switches to maximum defrost.
ECON Mode
In ECON (economy) mode, the A/C compressor is turned off. (Scheme 1) Temperature, blower speed and air distribution are automatically regulated. Air distribution is determined by difference between actual interior temperature and selected temperature.
AUTO Mode
When the AUTO button is pressed, the A/C compressor is turned on. (Scheme 1) Temperature, blower speed and air distribution are automatically regulated. Air distribution is determined by difference between actual interior temperature and selected temperature.
BI-LEV Mode
When BI-LEV (bi-level) button is pressed, the A/C compressor is turned on. (Scheme 1) Temperature, blower speed and air distribution are automatically regulated. Air distribution is fixed at center and footwell outlets.
DEFROST Mode
In this setting, temperature and blower speed are automatically regulated. (Scheme 1) All air is directed toward windshield.
HI & LO Settings
These settings are used to raise or lower blower speed in all operating modes. The HI or LO settings are canceled by pressing another mode button. (Scheme 1)
Scheme 1
A/C PROGRAMMER
The A/C programmer receives input signals from A/C-heater control panel. The programmer contains 5 solenoids which operate the vacuum servos for air distribution and heater valve. Based on input signals, the programmer also switches on the A/C compressor, radiator fan and controls the servomotor for temperature regulation. The programmer is located behind right side of glove box.
A/C BLOWER CONTROL UNIT
The A/C blower control unit receives signal from A/C-heater control panel, and regulates the amount of power supplied to the fresh air blower motor accordingly. The A/C blower control unit is located on top of evaporator assembly. (Scheme 2)
AMBIENT TEMPERATURE SENSORS
Two sensors measure the outside air temperature and send input signals to the A/C-heater control panel. The A/C-heater control panel measures both sensor readings and uses the lowest temperature value to calculate correction factor for interior temperature regulation. One sensor is located in front of radiator, and the other is located in evaporator plenum chamber. (Scheme 2)
IN-CAR TEMPERATURE SENSORS
The in-car temperature sensors measure interior air temperature and send signals to the A/C-heater control panel. A small fan drives air over instrument panel sensor to ensure accurate measurement. One sensor is mounted on top of instrument panel, and the other is located next to front dome light.
REFRIGERANT LOW PRESSURE SWITCH
The refrigerant low pressure switch disengages A/C compressor clutch if refrigerant pressure drops below 15 psi (1.1 kg/cm 2 ). Switch is located in suction line from A/C accumulator. (Scheme 2)
Scheme 2
REFRIGERANT HIGH PRESSURE SWITCH
This switch controls operation of cooling fan 2nd stage. Switch closes when pressure reaches 200 psi (14.1 kg/cm 2 ). Switch is located in high pressure line to A/C compressor and is identified by Yellow or Green housing.
A/C HIGH PRESSURE CUT-OUT SENSOR
Sensor measures refrigerant pressure and sends resistance signal to A/C-heater control panel. If refrigerant pressure goes above 435 psi (30.6 kg/cm 2 ), the A/C-heater control panel will shut A/C compressor off to prevent system damage. The A/C high pressure cut-out sensor, located next to refrigerant high pressure switch, is identified by Red housing.
Note. Low pressure switch and both high pressure switches can be removed without discharging the system.
A/C THERMOSTAT
The A/C thermostat controls power supply to A/C compressor clutch relay to prevent ice from forming on evaporator. If evaporator temperature falls below 32°F (0°C), A/C thermostat switch opens, A/C compressor clutch relay opens, and A/C compressor clutch disengages. The A/C thermostat is located on evaporator housing, with its capillary tube inserted in evaporator.
ENGINE COOLANT OVERHEAT SWITCH
When coolant temperature is greater than 247°F (120°C), switch sends a ground signal to terminal No. 20 of A/C-heater control panel. The A/C-heater control panel then sends a signal to A/C programmer, which in turn disengages the A/C compressor clutch. The engine coolant overheat switch is part of the electronic thermoswitch, located on cylinder head coolant flange.
DISABLING SYSTEM
Disconnect negative battery cables and shield terminals. Locate Red single-pin connector below instrument panel, near steering column. Connector is labeled AIR BAG. Disconnect Red single-pin connector.
SYSTEM FUNCTIONAL CHECK
When all service work is completed, reconnect Red single-pin connector below instrument panel near steering column. Place ignition switch in RUN position. Ensure AIR BAG indicator light on instrument cluster comes on for about 10 seconds and then goes out. If light does not operate as indicated, air bag system needs to be serviced.
HEATER FLAP ADJUSTMENT
- Remove windshield wiper assembly. Remove heater box cover. Remove 5 screws and servomotor cover with gasket attached. Turn ignition switch on. Set A/C control panel to HI. Select diagnosis channel 8. A value of 9-14 will be displayed. The correct value is 12. See «ACCESSING MEMORY FAULT CHANNEL»(/audi/200/c3-1988-1991/remont/automatic-hvac-system/#ac-heater-system-automatic__accessing-memory-fault-channel) under TROUBLE SHOOTING.
- To adjust, insert screwdriver through hole in servomotor housing. Turn screwdriver clockwise to decrease value or counterclockwise to increase value. (Scheme 3)
Scheme 3
ACCESSING MEMORY FAULT CHANNEL
Note. While information is being displayed on A/C-Heater control panel, the A/C system will run in the last mode selected.
- Start engine and operate A/C-heater system in AUTO mode. Simultaneously press and hold OUTSIDE TEMP and OFF buttons. Release OUTSIDE TEMP button then release OFF button. Display panel should read 01. Fault channel numbers are displayed with a short vertical line before first fault channel number.
- Pressing the WARMER button will advance display of fault channel by one. Each time WARMER button is pressed, system will advance to next fault channel until last number is reached, and then return to 01. Pressing the COOLER button decreases fault channel number by one. Memory fault channels are not trouble codes, but do identify individual circuits. (Scheme 4)and (Scheme 5).
- To exit fault display, turn ignition off or push any one of the mode buttons.
ACCESSING FAULT CODE
Access memory fault channel numbers. See ACCESSING MEMORY FAULT CHANNEL under TROUBLE SHOOTING. While display is in any channel number, press OUTSIDE TEMP button. If no fault code is present in memory, display panel will change to previous channel number. If a fault code is present, fault code (a number other than previous channel number) will be displayed. Circuit or sensor of that channel number is faulty. (Scheme 6)
Scheme 4
Scheme 5
Scheme 6
A/C-HEATER CONTROL PANEL
| WARNING | To avoid accidental air bag deployment, see AIR BAG DEACTIVATION SERVICING PRECAUTIONS in this article. |
Pry off A/C heater control panel cover. Remove 2 A/C control panel-to-console screws. Remove A/C control panel from console. To install, reverse removal procedure. Inspect A/C-heater control panel electrical connectors and contacts for damage.
Fresh Air Blower Removal
Remove heater box, see HEATER/EVAPORATOR BOX REMOVAL below. Remove blower cooling hose. Remove lock ring, stop washer and grommet.
Scheme 7
Fresh Air Blower Installation
Note. Before installing fresh air blower guides, lubricate with Vaseline.
To install simply follow the same steps as Removal, but in reverse order.
Heater/Evaporator Box Removal
Remove water box cover under hood. Remove windshield wiper assembly. Remove center console. Remove cap from engine coolant overflow bottle. Remove heater retaining band (arrow 1) in (Scheme 8). Clamp off heater hoses to heater core and remove (arrows in (Scheme 8). Remove all retainers between body and heater. Remove heater box.
Scheme 8
Heater/Evaporator Box Installation
Note. Before installing heater box, always replace self-adhesive gasket. When connecting water hoses, the lower connection on heater core is connected to the hose going to the water pump.
To install simply follow the same steps as Removing, but in reverse order.
Removal
- From engine compartment, loosen water drain hose retainer and push hose into plenum chamber. Disconnect vacuum unit hose and thermostat wires. Discharge A/C system using approved refrigerant recovery/recycling equipment. Remove refrigerant hoses and plug openings.
- From inside vehicle, remove lower dash panel. Remove 4 evaporator housing screws around air vent on evaporator unit.
- From engine compartment, carefully loosen assembly. Pull evaporator assembly up toward center of vehicle to remove. Separate housing halves to service evaporator.
Installation
Assemble evaporator case. Insert assembly into plenum chamber. Place drain hose through hole without kinking it, and clamp hose into place. Attach refrigerant lines loosely, and cement gasket into place around opening. Install screws. Tighten hoses, and recharge system. (Scheme 9)
Scheme 9
- Disconnect battery cable and thermostat wiring. Remove windshield wiper assembly and evaporator-heater duct clamp.
- Remove electrical wiring. Loosen restraining strap, and remove coolant reservoir cap. Clamp heater hoses closed near heater core. Disconnect hoses from core. Upper hose goes to water pump, and lower hose goes to cylinder head.
- From inside vehicle, disconnect vacuum lines. Disconnect air ducts and electrical wiring. Remove 4 screws around evaporator housing opening. Lift heater assembly up into engine compartment. Remove grommet and control cable. Loosen clips and wiring harness.
To install, reverse removal procedure. Seal all air duct connections carefully to prevent air leaks.
TEMPERATURE FLAP SERVO
Remove windshield wiper assembly. Remove heater box cover. Remove 5 screws and servomotor cover with gasket attached. Disconnect electrical connector. Release linkage and note position of spacers for reassembly. Remove servomotor. To install, reverse removal procedure.
