1993 VOLKSWAGEN CORRADO Repair Manual

A/C-HEATER SYSTEM - MANUAL
Article Text (p. 2)
1993 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Wednesday, March 22, 2000 08:49PM
* Disable air bag system before servicing any air bag system or
steering column component. See DISABLING & ACTIVATING AIR BAG
SYSTEM.
* Because of critical operating requirements of system, DO NOT
attempt to service any air bag system component.
* DO NOT leave air bag parts unattended. Install parts in vehicle
immediately after obtaining.
* DO NOT use air bag components that have been dropped from height
of more than 18 inches.
* DO NOT allow chemical cleaners, oil and grease to contact vinyl
covering on air bag unit.
* DO NOT place stickers or covers on steering wheel.
* Always disable air bag system before performing electric welding
on vehicle.
* Air bag system can only be tested using Diagnostic Tester (VAG
1551) and Multimeter (US-1119). Never use test light on air bag
system.
* DO NOT expose air bag unit to temperatures greater than 194øF
(90
øC).
DISABLING & ACTIVATING AIR BAG SYSTEM
WARNING: System voltage is retained for about 20 MINUTES after system
is deactivated. Wait about 20 MINUTES after system is
disabled before servicing, as air bag may accidentally
deploy, causing personal injury.
Disabling & Activating System
To disable system, disconnect negative battery cable. Wait 20
MINUTES before working on vehicle. To activate system, reconnect
negative battery cable. Verify system is functioning properly. See
SYSTEM OPERATION CHECK.
CAUTION: When battery is disconnected, radio will go into anti-theft
protection mode. Obtain radio anti-theft protection code
from owner prior to servicing vehicle.
DESCRIPTION
The air conditioning system is a cycling clutch type.
Compressor is cycled on and off by a thermostatic switch to maintain
constant cooling rate. System components include evaporator, expansion
valve, receiver-drier, control panel and condenser. A dual-pressure
switch includes a high-pressure cut-out switch and a low-pressure cut-
out switch.
Control panel includes 3 rotary knobs over 2 push buttons.
See Fig. 1. Left knob controls the fan and increases fan speed when
turned clockwise. Center knob is the temperature control and increases
heat by turning clockwise. Right knob controls air distribution.
The 2 push buttons are ON/OFF switches controlling A/C. Left
button controls normal A/C (outside air). Right button gives maximum
A/C using recirculating air. See Fig. 1.

A/C-HEATER SYSTEM - MANUAL
Article Text (p. 3)
1993 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Wednesday, March 22, 2000 08:49PMFig. 1: View Of A/C-Heater Control Panel (Corrado Similar)
Courtesy of Volkswagen United States, Inc.
OPERATION
SYSTEM CONTROLS
Air Distribution
Air distribution control knob directs airflow. With knob at 7
o'clock position, floor vents are open. With knob at 10 o'clock
position, defrost vents are open. At 2 o'clock position dash vents are
open. At 5 o'clock position, floor and dash vents are open.
Fan Speed Control
Fan switch increases fan speed when turned clockwise.
Temperature Control Knob
Temperature control knob increases heat by turning clockwise
and increases cooling by turning counterclockwise.
DUAL-PRESSURE SWITCH
High-Pressure Cut-Out Switch
This switch shuts compressor off if high pressure reaches
about 464 psi (32.6 kg/cmý). High-pressure cut-out switch will reset
when pressure decreases to about 348 psi (24.5 kg/cm
ý).
Low-Pressure Cut-Out Switch
This switch shuts compressor off when pressure in system is

A/C-HEATER SYSTEM - MANUAL
Article Text (p. 4)
1993 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Wednesday, March 22, 2000 08:49PM
too low. This protects compressor if not enough refrigerant is in
system. Low-pressure cut-out switch shuts compressor off at about 29
psi (2.0 kg/cmý).
THERMOSWITCH
Thermoswitch shuts compressor off if coolant temperature is
greater than 248
øF (120øC).
ADJUSTMENTS
AIR DISTRIBUTION CONTROL
1) Move air distribution control knob to defrost position.
Connect 3-foot long control cable to footwell/defrost flap lever. Push
flap lever toward cable and secure cable sheath with retainer clip.
2) Move air distribution control knob to panel (vent)
position. Connect 2-foot long control cable to center flap lever. Push
flap lever away from cable and secure cable sheath with retainer clip.
TEMPERATURE CONTROL
Move temperature knob to full cool position. Connect
temperature control cable (Blue sheath) to temperature flap lever.
Push flap lever away from cable and secure cable sheath with retainer
clip.
TROUBLE SHOOTING
NO COOLING
1) Ensure blower fan motor operates in all 4 speeds. Ensure
air duct closes off outside air and heater water valve is closed.
Clean condenser.
2) Inspect receiver-drier pressure seal. If seal is good, go
to step 3). If seal is broken, replace seal. Evacuate and recharge
system. If system cools properly, testing is complete. If system does
not cool, connect pressure gauges.
3) Adjust engine speed to 2500 RPM. Set controls for maximum
cooling and high fan. Insert thermometer in left air duct and close
all other ducts. With vehicle in shade, close windows and doors and
connect pressure gauges. Operate system for 10 minutes.
4) If fan does not operate, replace pressure switch. Ensure
system is okay. If fan does come on, turn engine off, and check for
condenser obstructions and blocked airflow.
5) Turn air conditioner on and off with temperature control.
Ensure compressor clutch engages. Push lever to extreme right position
and back again. A click should be heard from compressor clutch. If a
click is not heard, check for voltage at clutch coil wire with switch
on. If voltage is present, replace clutch coil. If voltage is not
present, check wiring or replace thermostatic switch.
6) If compressor clutch operates, check gauge readings. If

A/C-HEATER SYSTEM - MANUAL
Article Text (p. 5)
1993 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Wednesday, March 22, 2000 08:49PM
both gauges read too low, locate leak and recharge system. If both
gauges read too high, replace expansion valve. If low side is too high
and high side is too low, replace compressor.
INSUFFICIENT COOLING
1) Ensure blower fan motor operates at all 4 speeds. Ensure
air duct closes off outside air intake and heater water valve is
closed. Clean condenser.
2) Adjust engine speed to 2500 RPM. Set controls for maximum
cooling and high fan. Insert thermometer in left air duct and close
all other ducts. With vehicle in shade, close windows and doors and
connect pressure gauges. Operate system for 10 minutes.
3) If both gauges read too high, replace expansion valve. If
both gauges read low, locate leak and recharge system. If both gauge
readings are normal, go to next step. If high side is too high and
suction side is normal, go to step 5). If high side is too low and
suction side is too high, go to step 6). If high side is normal and
suction side is too low, go to step 7).
4) Turn compressor off and observe gauges. If readings
equalize in 30 seconds, replace compressor. If readings take longer to
equalize, ensure capillary tube installed length is 13" (330 mm).
5) If capillary tube installation is correct, run system at
maximum cooling for 15 minutes. If thermometer indicates temperature
is less than 36øF (2øC) when compressor is turned off, or temperature
is greater than 48
øF (9øC) with compressor on, replace thermostatic
switch.
6) Check condenser fins and clean or straighten. If operation
is still not correct, discharge system until bubbles appear in sight
glass. Recharge system until bubbles disappear, and recheck pressures.
If operation is still incorrect, locate leaks and tighten fittings.
Discharge A/C system using approved refrigerant recovery/recycling
equipment. Evacuate system to remove all air and recharge system.
7) Check for bubbles at sight glass. If bubbles are present,
repair leaks and recharge system. If no bubbles are present, check
condenser-to-expansion valve line for kinks and repair if necessary.
Check line (from condenser to expansion valve) for restrictions by
feeling line for cold spots. If there are no cold spots, replace
expansion valve.
8) If cold spot is felt, remove and flush out lines and
condenser. Check for bubbles at sight glass. If there are no bubbles
present, replace compressor. If bubbles are present, check for leaks.
Repair and recharge system.
INTERMITTENT COOLING
1) Ensure blower fan motor operates in all 4 speeds. Ensure
air duct closes off outside air and heater water valve is closed.
Clean condenser.
2) Adjust engine speed to 2500 RPM. Set controls for maximum
cooling and high fan. Insert thermometer in left air duct and close
all other ducts. With vehicle in shade, close windows and doors and

A/C-HEATER SYSTEM - MANUAL
Article Text (p. 6)
1993 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Wednesday, March 22, 2000 08:49PM
connect pressure gauges. Operate system for 10 minutes.
3) Check for cool air from left duct. Low pressure gauge
should read more than 16 psi (1.1 kg/cmý). If low pressure gauge
reading is incorrect, place hands around expansion valve to warm
valve. If pressure rises, moisture is present in system. Discharge A/C
system using approved refrigerant recovery/recycling equipment.
Evacuate and recharge system. If pressure does not rise, go to next
step.
4) Check temperature on thermometer when thermostatic switch
turns compressor off. If temperature is 39
øF (4øC), system is okay. If
temperature is lower than 39
øF (4øC), ensure capillary tube installed
length is 13" (330 mm). If capillary tube installation is correct,
replace thermostatic switch.
TESTING
A/C SYSTEM PERFORMANCE
1) Park vehicle out of direct sunlight. Start engine and
operate engine at 2500 RPM. Set A/C controls to outside air, panel
(vent) mode, full cold, and A/C button on.
2) Set blower/fan on high speed and open windows. Operate
system for 6-7 minutes to allow system to stabilize. Insert
thermometer in center vent, and measure temperature. Temperature at
center vent must be 19-40
øF (-7 to 4øC) at center vent, with high side
and low side pressures within specification. See SPECIFICATIONS table
at beginning of article.
AMBIENT TEMPERATURE SWITCH
1) Remove air intake grille from right side cowl. Remove
switch from panel on right side of tray area. Place switch in freezer.
2) Using a DVOM, check switch resistance. Switch resistance
must be infinite (no continuity) below 30
øF (-1øC). Allow switch to
warm above 45
øF (7øC). Switch resistance must be zero ohms
(continuity). Replace switch if necessary.
COMPRESSOR CLUTCH COIL
Disconnect compressor clutch harness connector. Check
resistance between clutch connector terminals. Resistance reading
should be 3.6 ohms. If resistance reading is not as specified, replace
clutch coil.
DUAL-PRESSURE SWITCH
High-Pressure Cut-Out Switch
Locate dual-pressure switch on refrigerant line (right strut
tower). Switch is identified by its 4 wires. Ensure switch opens at
464 psi (32 kg/cm
ý). Ensure switch closes at 348 psi (24 kg/cmý).
NOTE: Dual-pressure switch may be removed without discharging

A/C-HEATER SYSTEM - MANUAL
Article Text (p. 7)
1993 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Wednesday, March 22, 2000 08:49PM
refrigerant from A/C system.
Low-Pressure Cut-Out Switch
Locate A/C pressure switch on refrigerant line (right strut
tower). Switch is identified by its 4 wires. Ensure switch opens below
29 psi (2.0 kg/cmý). Ensure switch closes above 43.5 psi (3.0 kg/cmý).
Replace switch if necessary.
REMOVAL & INSTALLATION
WARNING: To avoid injury from accidental air bag deployment, read and
carefully follow all SERVICE PRECAUTIONS and DISABLING &
ACTIVATING AIR BAG SYSTEM procedures.
A/C-HEATER CONTROL PANEL
Removal & Installation
Remove control panel trim. Remove control panel mounting
screws and pull cover forward out of dashboard. Disconnect harness
connector and control cables. Remove A/C-heater control panel. To
install, reverse removal procedures.

A/C-HEATER SYSTEM - MANUAL
Article Text (p. 8)
1993 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Wednesday, March 22, 2000 08:49PMFig. 2: Exploded View Of A/C-Heater System
Courtesy of Volkswagen United States, Inc.

A/C-HEATER SYSTEM - MANUAL
Article Text (p. 9)
1993 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Wednesday, March 22, 2000 08:49PM
BLOWER MOTOR
Removal & Installation
Disconnect blower motor harness connector. Depress blower
motor retainer clip and rotate blower motor clockwise to disengage lug
on blower motor from clip. To install, reverse removal procedure.
COMPRESSOR
Removal & Installation
Remove ribbed belt. Discharge A/C system using approved
refrigerant recovery/recycling equipment. Remove hoses and plug.
Remove compressor. To install, reverse removal procedure.
EVAPORATOR & HEATER CORE
Removal & Installation
Discharge A/C system using approved refrigerant
recovery/recycling equipment. Drain coolant. Remove instrument panel.
See INSTRUMENT PANEL. Remove support bracket and evaporator/heater
housing assembly. Remove evaporator and/or heater core. See Fig. 3..
To install, reverse removal procedure.Fig. 3: Exploded View Of Evaporator Housing
Courtesy of Volkswagen United States, Inc.