1990 VOLKSWAGEN CORRADO Repair Manual

HEATER SYSTEM
Article Text (p. 5)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PM
retaining screws. Remove lower left instrument panel. Remove lower
right instrument panel tray retaining screws.
2) Remove lower right instrument panel. Remove gearshift
lever knob. Remove gearshift lever boot. Remove center console
retaining screws. Slide center console rearward. Disconnect electrical
connectors attached to center console. Remove center console.
3) Remove temperature control knobs. Remove trim plate.
Remove radio. Remove switches from instrument panel. Remove instrument
panel trim plate retaining screws. Remove instrument panel trim plate.
Remove instrument cluster retaining screws. Remove instrument cluster.
4) Disconnect speedometer cable, electrical connectors and
vacuum hoses from instrument cluster. Remove speaker grilles. Remove
air outlet grilles from housings. Remove housing retaining screws.
Remove air outlet housings. Remove instrument panel mounting nuts and
screws.
5) Remove instrument panel. Disconnect heater hoses from
heater core. Remove heater assembly mounting bolts and nuts. Remove
all attaching ducts. Disconnect cables from heater assembly. Remove
heater assembly.
INSTALLATION
Reverse removal procedure for installation. Fill radiator
with coolant and start engine. Ensure heater control is in warm
position to purge air from heater core.
WIRING DIAGRAMSFig. 4: Heater System Wiring Diagram (Cabriolet)Fig. 5: Heater System Wiring Diagram (Corrado)

HEATER SYSTEM
Article Text (p. 6)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PMFig. 6: Heater System Wiring Diagram (Fox)Fig. 7: Heater System Wiring Diagram (Golf GL, GTI, Jetta & Jetta
GLi)Fig. 8: Fresh Air Blower Motor Wiring Diagram (Vanagon)Fig. 9: Warm Air Blower Motor Wiring Diagram (Vanagon)

HEATER SYSTEM
Article Text (p. 7)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PM
END OF ARTICLE

I - SYSTEM/COMPONENT TESTS
Article Text
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:46PM
ARTICLE BEGINNING
1990 ENGINE PERFORMANCE
Systems & Component Testing
Volkswagen; Cabriolet, Corrado, Fox, Golf GL/GTI,
Jetta, Vanagon
INTRODUCTION
Before testing separate components or systems, perform
procedures in F - BASIC TESTING and H - TESTS W/O CODES articles.
NOTE: Testing individual components does not isolate shorts or
opens. Perform all voltage tests with a Digital
Volt-Ohmmeter (DVOM) with a minimum 10-megohm input
impedance, unless stated otherwise in test procedure. Use
ohmmeter to isolate wiring harness shorts or opens.
AIR INDUCTION SYSTEMS (SUPERCHARGER)
BOOST PRESSURE
1) Before checking supercharger boost pressure, ensure engine
idle speed is correct. See D - ADJUSTMENTS article. Ensure engine oil
temperature is 176øF (80øC). Check knock sensor operation. See KNOCK
SENSOR under IDLE CONTROL SYSTEM in this article.
2) Connect Pressure Gauge (VW1397) or equivalent to the
pressure regulator hose using adapter "T". Open pressure gauge check
valve to position "A" and start engine.
3) Remove harness connector from CO potentiometer and Blue
connector from temperature sensor (in front flange on cylinder head).
Accelerate to full throttle. Engine speed must increase periodically
then drop (surge). Watch pressure gauge, boost pressure must reach 8.7
psi (0.6 kg/cm
ý). If boost does not reach specification, check for
leaks in air system and correct by-pass valve setting. Check
supercharger.
COMPUTERIZED ENGINE CONTROLS
NOTE: For fuel system used on model being tested, see FUEL SYSTEM
APPLICATION table.
FUEL SYSTEM APPLICATION
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄApplication Fuel System
Cabriolet, Corrado, Golf GL/GTI,
Jetta & Vanagon .................................. AFC-Digifant II
Fox .......................................................... CIS-E
Jetta GLi ............................................. CIS-Motronic

I - SYSTEM/COMPONENT TESTS
Article Text (p. 2)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:46PMÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ CONTROL UNIT (AFC-DIGIFANT II)
NOTE: Before checking ECU terminal voltages, check all terminals
and connections for looseness or presence of corrosion.
Repair as needed, before continuing.
GROUND CIRCUITS
Using Multimeter (US 1119), check resistance of ground
connections for ECU. Remove ECU connector. Check continuity to ground
on terminals No. 13 and 19. See L - WIRING DIAGRAMS for terminal
identification. Resistance should be zero ohms. If resistance is not
zero ohms, repair open or short in wiring.
POWER CIRCUITS
1) Turn ignition off. Disconnect ECU connector. Using a
voltmeter, turn ignition on and check for battery voltage between ECU
connector terminals No. 13 (negative) and No. 14 (positive). See L -
WIRING DIAGRAMS for terminal identification and wire colors. If
battery voltage is not present, repair wiring as required.
2) Check terminals No. 13 (negative) and No. 1 (positive) for
battery voltage. If battery voltage is not present, check fuse No. 18
on fuse block. If fuse is okay, check wiring from ECU connector to
fuse box for open.
CONTROL UNIT (CIS-E)
GROUND CIRCUITS
Using Multimeter (US 1119), check resistance of ground
circuits for ECU. Remove ECU connector. Check continuity to ground on
terminals No. 2 and No. 9. Resistance should be zero ohms. If
resistance is not zero ohms, repair open or short in wiring.
POWER CIRCUITS
Turn ignition off. Disconnect ECU connector. Using a
voltmeter, turn ignition on and check for battery voltage between ECU
connector terminals No. 2 (negative) and No. 1 (positive). See L -
WIRING DIAGRAMS for terminal identification and wire colors. If
battery voltage is not present, check fuse No. 23 on fuse block. If
fuse is okay, check CIS-E ECU connector to fuse box wiring for open.
CONTROL UNIT (CIS-MOTRONIC)
GROUND CIRCUITS
Using Multimeter (US 1119), check resistance of ground

I - SYSTEM/COMPONENT TESTS
Article Text (p. 3)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:46PM
circuits to ECU. The ECU engine ground is near ignition distributor.
Remove ECU connector. Check resistance to ground on terminal No. 35.
Resistance should be zero ohms. If resistance is not zero ohms, repair
open or short in wiring.
POWER CIRCUITS
Turn ignition off. Disconnect ECU connector. Using a
voltmeter, check terminals No. 12, 14, 19 and 34 for battery voltage.
If battery voltage is not present. Check fuses No. 15, 18 and 24. If
fuses are okay, check for open in wiring between ECU and fuse box. See
L - WIRING DIAGRAMS for terminal identification and wire colors.
ENGINE SENSORS & SWITCHES
AIRFLOW SENSOR (FOX & JETTA GLI)
1) Start engine to pressurized fuel system. Turn engine off
and remove intake boot from top of airflow sensor. Disconnect coil
secondary wire from coil and jumper to ground.
2) Check sensor play by slowly moving sensor plate through
travel range with a magnet. See Fig. 1. Resistance should be felt.
Move plate back to the rest position. There should be no resistance.
If binding is felt, loosen sensor plate hold-down bolt and adjust
plate to center of venturi.
3) If resistance is uneven, remove airflow sensor from
housing to clean and lubricate lever assembly. If resistance is caused
by control plunger, remove and clean control plunger assembly. If
binding continues, replace fuel distributor.
4) Check position of airflow sensor plate. Airflow sensor
plate edge must be within .075" (1.9 mm) below the narrowest section
of the venturi. If not, bend sensor spring until correct specification
is obtained. Ensure a small gap exists between sensor lever and
control plunger.Fig. 1: Identifying Airflow Sensor Components (Fox & Jetta GLi)
Courtesy of Volkswagen United States, Inc.
AIRFLOW SENSOR (GOLF & JETTA)
1) Start engine to pressurized fuel system. Turn engine off

I - SYSTEM/COMPONENT TESTS
Article Text (p. 4)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:46PM
and remove intake boot from top of airflow sensor. Check sensor plate
by lifting plate through travel cycle with magnet or pliers.
2) Continuous resistance should be felt. Move plate back to
rest position. There should be no resistance. If resistance is felt,
replace airflow sensor. If sensor plate lever is difficult to move
upward but moves freely downward, check sensor plate for correct
centering.
3) Sensor plate should be evenly centered in the housing with
plate edge at the narrowest section of the venturi while at rest
position. If sensor plate adjustment is correct, check control plunger
for sticking. If control plunger is sticking, replace fuel distributor
assembly.
AIRFLOW SENSOR (VANAGON)
1) Turn ignition off. Remove Electronic Control Unit (ECU)
connector. Attach ohmmeter to ECU connector. See Fig. 3. Resistance
should correspond to ECU PIN CHECK in AFC-DIGIFANT II AIRFLOW SENSOR
RESISTANCE table.
2) With ignition off, unplug connector from airflow sensor.
Attach ohmmeter to airflow sensor terminal. See Fig. 2. Resistance
should correspond to AIRFLOW SENSOR PIN CHECK in AFC-DIGIFANT II
AIRFLOW SENSOR RESISTANCE table.
AFC-DIGIFANT II AIRFLOW SENSOR RESISTANCEÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄTerminal Ohms
ECU Pin Check
No. 6 & No. 17 .......................................... 500-1000
No. 17 & No. 21 .............................................. (1)
Airflow Sensor Pin Check
No. 3 & No. 4 ........................................... 500-1000
No. 2 & No. 3 ................................................ (1)
(1) - Resistance should fluctuate as sensor door is moved.
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄFig. 2: Identifying AFC-Digifant II Airflow Sensor & Terminals
Courtesy of Volkswagen United States, Inc.

I - SYSTEM/COMPONENT TESTS
Article Text (p. 5)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:46PM
COOLANT TEMPERATURE SENSOR
Turn ignition off. Use a thermometer to measure coolant
temperature. Unplug connector from Electronic Control Unit (ECU).
Attach an ohmmeter between terminals No. 6 and No. 10 of ECU
connector. See Fig. 3. Resistance should decrease as coolant
temperature increases. See COOLANT TEMPERATURE SENSOR RESISTANCE
table. Replace sensor if resistance is not within specification.
COOLANT TEMPERATURE SENSOR RESISTANCEÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄTemperature Ohms
68
øF (20øC) .............................................. 2200-2700
158
øF (70øC) ............................................... 400-480
194
øF (90øC) ............................................... 210-280
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄFig. 3: Identifying ECU Connector Terminals
Courtesy of Volkswagen United States, Inc.
HALL EFFECT SENDER
For Hall Effect sender testing, see F - BASIC TESTING
article.
OXYGEN SENSOR (ALL MODELS EXCEPT VANAGON)
1) Ensure exhaust system is not leaking. Warm engine to
normal operating temperature with all accessories off. Remove
differential pressure regulator connector. Connect Wiring Harness
Adapter (VW 1315 A/1) in series. See Fig. 4.
2) Attach Multimeter (US 1119) to adapter and set meter on
DCA 200m scale. Remove PCV hose and vent to atmosphere. Remove 90
degree "T" connector and insert port with small vent hole into intake
air boot. See Fig. 5.
3) Start engine and allow to run for 2 minutes. Meter reading
should start fluctuating. If reading does not fluctuate, raise engine
speed to 3000 RPM. If meter reading fluctuates, oxygen sensor is okay.
If reading still does not fluctuate, check control unit and wiring
harness for short or open circuit.
OXYGEN SENSOR (VANAGON)
1) Ensure pressure regulator is functional and engine is at
normal operating temperature. Start engine and allow to run for 2