1.8L Turbo & 2.8L V6
A/C pressure switch is a combination switch (two switching components) that protects refrigerant circuit components from malfunctioning due to excessive or insufficient refrigerant system pressures. Switch part between terminals 1 and 2 switches off the A/C clutch when the system pressure is too high or when there is not enough refrigerant in the system. Switch part between terminals 3 and 4 switches coolant fan to second fan speed when system pressures increase. (Scheme 8)
AFTER-RUN ELECTRIC COOLANT PUMP
Note. As a running change in model year 1999, models with 2.8L V6 engines are equipped with an After Run Electric Coolant Pump. Pump is operated by Coolant Fan Control Module based on a signal from Coolant Fan Control Thermo Switch. Coolant After-Run Pump and After-Run Fan are controlled by same control module.
2.8L V6
Models with 2.8L V6 engines are equipped with an After Run Electric Coolant Pump. Pump is operated by the Coolant Fan Control Module based on a signal from the coolant fan control thermo switch.
The After-Run Coolant Pump is generally activated for 3-10 minutes about 15 seconds after ignition is shut off. If the coolant temperature is above 195°F (91°C) the coolant fan will also be turned on.
1.8L Turbo
Coolant Fan Control Thermo Switch is a 2-stage thermo switch. Coolant Fan Control Thermo Switch, stage 1 sends a signal to the first speed coolant fan relay, which turns the fan on to first speed. Stage 2 sends a signal to the second speed coolant fan relay, which turns the fan on to second speed.
2.8L V6 (1997-12/1998)
Coolant Fan Control Thermo Switch is a 2-stage thermo switch. Coolant Fan Control Thermo Switch, stage 1 sends a signal to the first speed coolant fan relay, which turns the fan on to first speed. Stage 2 sends a signal to the second speed coolant fan relay, which turns the fan on to second speed.
2.8L V6 (1/1999-2000)
Coolant Fan Control Thermo Switch is a 2-stage thermo switch. Thermo switch signals the coolant fan control module to activate the coolant fans.
COMPONENT LOCATIONS
| Component | Location | |
|---|---|---|
| A/C Pressure Switch | Right Front Corner Of Engine Compartment. (Scheme 1) | |
| After Run Coolant Pump (2.8L V6) | Lower Right Side Of Engine, Above Generator. (Scheme 2) | |
| Climatronic (Auto A/C) Control Module | Integrated With A/C Control Panel | |
| Coolant Fan Control Module | ||
| 2.8L V6 | Left Front Corner Of Engine Compartment. (Scheme 3) | |
| Coolant Fan Control Series Resistor (1.8L Turbo) | On Left Front Frame Rail, Bottom. (Scheme 4) | |
| Coolant Fan Ground Point | Left Lower A Pillar | |
| Coolant Fan Thermo Switch (1.8L Turbo) & 1997 (2.8L V6) | In Lower Left Corner Of Radiator. (Scheme 5) | |
| Coolant Fan Thermo Switch 1998 On (2.8L V6) | In Lower Right Corner In Radiator Hose/Tube Fitting Close To Radiator Tank. (Scheme 6) | |
| Eight-Fold Auxiliary Relay Panel | Under Left Side Of Dash, Behind Trim Panel | |
| First Speed Coolant Fan Relay (1) | In 8-Fold Auxiliary Relay Panel (Position No. 3). (Scheme 7) | |
| Second Speed Coolant Fan Control Relay (1) | In 8-Fold Auxiliary Relay Panel (Position No. 2). (Scheme 7) | |
| Fuse For Coolant Fan Relays (1) | In 8-Fold Auxiliary Relay Panel (Position No. 19). (Scheme 7) | |
| Fuse For Coolant Fan Control Relay Coils (1) | In 8-Fold Auxiliary Relay Panel (Position No. 21). (Scheme 7) | |
| (1) As a running change in model year 1999, models with 2.8L V6 engines are equipped with an After Run Electric Coolant Pump. Pump is operated by Coolant Fan Control Module based on a signal from Coolant Fan Control Thermo Switch. Coolant After-Run Pump and After-Run Fan (second speed) are controlled by same control module. Coolant Fan Control Module replaces Coolant Fan Relays and Coolant Fan Control Series Resistor is no longer used. | ||
| (1) | As a running change in model year 1999, models with 2.8L V6 engines are equipped with an After Run Electric Coolant Pump. Pump is operated by Coolant Fan Control Module based on a signal from Coolant Fan Control Thermo Switch. Coolant After-Run Pump and After-Run Fan (second speed) are controlled by same control module. Coolant Fan Control Module replaces Coolant Fan Relays and Coolant Fan Control Series Resistor is no longer used. |
COMPONENT LOCATIONS
Scheme 1
Scheme 2
Scheme 3
Scheme 4
Scheme 5
Scheme 6
Scheme 7
SYSTEM TESTS
System testing information is not available from manufacturer. To assist in circuit diagnosis, see WIRING DIAGRAMS . Ensure all fuses are okay before proceeding with any testing. If a fuse is blown, check for a short circuit and repair before replacing fuse.
Switch terminal Nos. 3 and 4 control coolant fan operation by the coolant fan control module. Fan speed increases to second speed when system pressure increases. Switch closes above 244 psi (16.8 bar), and opens again below 184 psi (12.7 bar).
Scheme 8
Switch terminal Nos. 3 and 4 control coolant fan operation by the coolant fan control module. Fan speed increases to second speed when system pressure increases. Switch closes above 244 psi (16.8 bar), and opens again below 184 psi (12.7 bar).
| Application & Terminal | Switch Condition | Temperature °F (°C) | ||
|---|---|---|---|---|
| 1.8L Turbo | ||||
| Stage One | ||||
| Terminal No. 2 | On | 197-206 (92-97) | ||
| Terminal No. 2 | Off | 183-195 (84-91) | ||
| Stage Two | ||||
| Terminal No. 1 | On | 210-221 (99-105) | ||
| Terminal No. 1 | Off | 195-208 (91-98) | ||
| (1) Check for battery voltage at specified terminal at indicated temperature, (on mode). | ||||
| (1) | Check for battery voltage at specified terminal at indicated temperature, (on mode). |
COOLANT FAN CONTROL THERMO SWITCH PERFORMANCE (1)
| Application & Terminal | Switch Condition | Temperature °F (°C) | ||
|---|---|---|---|---|
| 2.8L V6 (2) | ||||
| Stage One | ||||
| Terminal No. 2 | On | 197-206 (92-97) | ||
| Terminal No. 2 | Off | 183-195 (84-91) | ||
| Stage Two | ||||
| Terminal No. 1 (3) (4) | On | 210-221 (99-105) | ||
| Terminal No. 1 (3) (4) | Off | 195-208 (91-98) | ||
| (1) Check for battery voltage at specified terminal at indicated temperature. (2) Model year 1997 through 12/1998. (3) For 2.8L V6, starting in 1/1999 thermal fan switch is a 4 terminal switch. Each coolant fan stage having it's own ground, stage 1 terminal 1. Stage 2 terminal 3. (4) For 2.8L V6, starting in 1/1999 terminal No. 4 is used for activating coolant fan stage two. | ||||
| (1) | Check for battery voltage at specified terminal at indicated temperature. |
| (2) | Model year 1997 through 12/1998. |
| (3) | For 2.8L V6, starting in 1/1999 thermal fan switch is a 4 terminal switch. Each coolant fan stage having it's own ground, stage 1 terminal 1. Stage 2 terminal 3. |
| (4) | For 2.8L V6, starting in 1/1999 terminal No. 4 is used for activating coolant fan stage two. |
COOLANT FAN CONTROL THERMO SWITCH PERFORMANCE (1)
COOLANT FAN CONTROL MODULE
Information is not available from manufacturer.
AFTER-RUN COOLANT PUMP & FAN
| CAUTION | There is no wiring diagram available from the manufacturer for After-Run Electric Coolant Pump and After-Run Electric Coolant Pump Control Module. |
Scheme 9
- Fuse 34 must be OK. Fuse panel is behind access cover on far left side of dash. (Scheme 9)
- Start engine and idle briefly. Switch ignition off.
- After-run coolant pump must start after about 15 seconds. If pump does not run, disconnect 2-pin connector from pump. Attach multimeter for measuring voltage to contacts 1 and 2 of connector. Reading should be 11-15 V. If no voltage is present, go to step 6.
- If the voltage is corect, replace after run coolant pump. Remove noise insulation panel and drain coolant. (Scheme 10) See «2.8L 30-VALVE V6 (AHA & ATQ)»(/audi/a4/b5-1999-2001/remont/accessory-drive-belts/#cooling-system-specifications-drive-belt-routing__28l-30-valve-v6-aha-atq) article in ENGINE COOLING in ENGINES.
- Remove After-Run Pump. (Scheme 11) Installation is in reverse order.
- Check Cooling Fan and Coolant After-Run Pump Control Module harness connector for corrosion and good connection. (Scheme 3) Check Coolant Fan Control Thermo Switch harness connector for corrosion and good connection. (Scheme 6) Check A/C Pressure Switch harness connector for corrosion and good connection. (Scheme 1) If harness connections are okay, go to next step. If harness connections are not okay, repair as necessary.
- Check Coolant Fan Control Thermo Switch. (Scheme 6)and «COOLANT FAN CONTROL THERMO SWITCH PERFORMANCE»(/audi/a4/b5-1999-2001/remont/cooling-fan/#electric-cooling-fans) table, under COOLANT FAN CONTROL THERMO SWITCH 2.8 V6. If switch is okay go to next step. If switch is not okay, replace faulty switch.
Scheme 10
Scheme 11
TORQUE SPECIFICATIONS
| Application | Ft. Lbs. (N.m) |
|---|---|
| Coolant Fan Control Thermo Switch | 26 (35) |
| INCH Lbs. (N.m) | |
| A/C High Pressure Sensor or Switch | (1) 44 (5) |
| (1) A/C refrigerant does not need to be discharged. Use new "O" ring. | |
| (1) | A/C refrigerant does not need to be discharged. Use new "O" ring. |
TORQUE SPECIFICATIONS
1997
See in COOLING FAN SYSTEM WIRING DIAGRAMS in ELECTRICAL.
1998
See in COOLING FAN SYSTEM WIRING DIAGRAMS in ELECTRICAL.
1999
See in COOLING FAN SYSTEM WIRING DIAGRAMS in ELECTRICAL.
2000 1.8L Turbo
See in COOLING FAN SYSTEM WIRING DIAGRAMS in ELECTRICAL.
2000 2.8L V6
See in COOLING FAN SYSTEM WIRING DIAGRAMS in ELECTRICAL.
See also:
• 2.8L 30-VALVE V6 (AHA & ATQ)
• WIRING DIAGRAMS