Radiator Cooling Fan: Testing and Inspection
Electric coolant fan, checking
Special tools, testers and auxiliary items required
^ Multimeter V.A.G 1526 B or V.A.G 1526 A
^ Voltage tester V.A.G 1527 B
^ Connector test kit V.A.G 1594 C or V.A.G 1594 A
^ Test box V.A.G 1598/31
^ Vehicle Diagnostic, Testing and Information System VAS 5051 A with diagnostic cable VAS 5051/1
Work sequence
- Connect Vehicle Diagnostic, Testing and Information System VAS 5051 A and select vehicle system "01 - engine electronics". Ignition must be switched on Guided Fault Finding in VAS 5051 A.
Display on VAS 5051 A:
- In selection - 1 -, click on function "03 - output Diagnostic Test Mode (DTM)".
- Press -button repeatedly until coolant fan activation 2" is actuated.
^ Coolant Fan Control (FC) Control Module 2 -J671- switches on Coolant Fan 2 -V177- (right) one time slowly to full speed.
- Press -button repeatedly, until "coolant fan activation 1" is actuated.
Coolant Fan Control (FC) Control Module -J293- switches on Coolant Fan -V7- (left) one time slowly to full speed.
- End function "03 - output Diagnostic Test Mode (DTM)" by pressing button.
If fan activation does not react as described:
- Produce conditions for starting up coolant fan according to required input criteria (e.g. switch on A/C system, increase engine temperature correspondingly).
Display on VAS 5051 A:
- In selection - 1 -, click on function "08 - Read measuring value block".
Display on VAS 5051 A:
- Select function "135" in button field - 2 - for "display group 135" and press Q to confirm input.
Display on VAS 5051 A:
- Check indication in display fields - 2 - and - 3 -.
Note: At fan request by A/C system and/or coolant temperature greater than 98C, duty cycle must rise above 10% and fans must start up.
- Press button to end function "08 - Read measuring value block".
If duty cycle does not rise above 10%:
- Check DTC memory of Engine Control Module (ECM).
- Select "06 - End Output".
- Switch ignition off.
- Repair displayed malfunctions if necessary.
If the respective fan does not start up even though duty cycle is above 10%:
- Check Coolant Fan -V7-
Checking Coolant Fan -V7- (left)
^ Fuses for Coolant Fan -V7- and Coolant Fan Control (FC) Control Module -J293- OK Electrical Wiring Diagrams, Troubleshooting Component Locations.
- Remove cover - 1 - in engine compartment (left side).
- Remove electrical harness connector - 1 - from bracket and disconnect it.
- Connect multimeter for voltage measurement as follows.
^ Specified value: approximately battery voltage respectively
If specified values are not obtained:
- Repair wiring connection if necessary.
If specified values are obtained:
- Connect multimeter for voltage measurement as follows:
^ Specified value: approximately battery voltage If specified value is not obtained:
- Repair wiring connection if necessary.
If specified value is obtained:
- Connect multimeter between terminal - 2 - and - 3 - of harness connector for voltage measurement.
^ Vehicle Diagnostic, Testing and Information System VAS 5051 A connected, "Vehicle Self-Diagnosis" "01 Engine electronics" selected. Ignition must be switched on for this.
Display on VAS 5051 A:
- In selection - 1 -, click on function "03 - output Diagnostic Test Mode (DTM)".
- Press -button repeatedly, until "coolant fan activation 1" is actuated.
^ Voltage value must decrease slowly from approximately battery voltage to approximately 8 volts (and then increase again).
- End function "03 - output Diagnostic Test Mode (DTM)" by pressing button.
- Select "06 - End Output".
- Switch ignition off.
If specified value is not obtained:
- Connect test box V.A.G 1598/31 to wiring harness connectors, Engine Control Module (ECM) is not connected. Connect Ground (GND) clip at test box (not visible in illustration) to Ground (GND).
CAUTION: To avoid damaging electronic components, set measuring range before connecting test leads and observe all test requirements.
Check following wiring connection for open circuit and short circuit to Ground (GND) and B+:
Repair wiring connection if necessary. If no malfunctions are detected:
- Remove front bumper cover.
- Connect multimeter with measuring probes and connector adapters from connector test kit V.A.G 1594 C between terminal - 1 - and terminal - 2 - of brown harness connector on Coolant Fan Control (FC) Control Module -J293-; harness connector remains connected.
^ Vehicle Diagnostic, Testing and Information System VAS 5051 A connected, "Vehicle Self-Diagnosis" "01 Engine electronics" selected. Ignition must be switched on.
Display on VAS 5051 A:
- In selection - 1 -, click on function "03 - output Diagnostic Test Mode (DTM)".
- Press button repeatedly until "coolant fan activation 1" is actuated.
^ Voltage value must increase up to approximately 10.5 volts (and then decrease again).
- End function "03 - output Diagnostic Test Mode (DTM)" by pressing button.
- Select "06 - End Output".
- Switch ignition off.
If specified value is reached but fan does not run:
- Replace Coolant Fan -V7-
If specified value is not obtained:
- Check wiring connections from harness connector at left front in engine compartment to Coolant Fan Control (FC) Control Module -J293- according to wiring diagram.
If no malfunctions are detected:
- Replace Coolant Fan Control (FC) Control Module -J293-.
Checking Coolant Fan 2 -V177- (right)
^ Fuses for Coolant Fan 2 -V177- and Coolant Fan Control (FC) Control Module 2 -J671- OK Electrical Wiring Diagrams, Troubleshooting Component Locations.
- Remove front bumper cover.
- Connect multimeter with measuring probes and connector adapters from connector test kit V.A.G 1594 C between terminal - 1 - and terminal - 2 -; harness connector for Coolant Fan 2 -V177- remains connected.
^ Vehicle Diagnostic, Testing and Information System VAS 5051 A connected, "Vehicle Self-Diagnosis" "01 Engine electronics" selected. Ignition must be switched.
Display on VAS 5051 A:
- In selection - 1 -, click on function "03 - output Diagnostic Test Mode (DTM)".
- Press -button repeatedly until coolant fan activation 2" is actuated.
^ Voltage value must increase up to approximately 9 volts
- End function "03 - output Diagnostic Test Mode (DTM)" by pressing button.
- Select "06 - End Output".
- Switch ignition off.
If specified value is reached but fan does not run:
- Replace Coolant Fan 2 -V177-
If specified value is not obtained:
- Bring lock carrier into service position [1][2]Procedures
- Remove Coolant Fan Control (FC) Control Module 2 -J671- from left front longmember - arrows -.
- Disconnect electrical harness connector - 2 - on Coolant Fan Control (FC) Control Module 2 -J671-.
- Connect multimeter for voltage measurement as follows.
Specified value: approximately battery voltage respectively
If specified values are not obtained:
- Repair wiring connection if necessary.
If specified values are obtained:
- Disconnect electrical harness connector - 1 - on Coolant Fan Control (FC) Control Module 2 -J671-.
- Connect multimeter between terminal - 1 - and - 2 - of harness connector for voltage measurement.
^ Vehicle Diagnostic, Testing and Information System VAS 5051 A connected, "Vehicle Self-Diagnosis" "01 Engine electronics" selected. Ignition must be switched on.
Display on VAS 5051 A:
- In selection - 1 -, click on function "03 - output Diagnostic Test Mode (DTM)".
- Press button repeatedly until "coolant fan activation 2" is actuated.
^ Voltage value must decrease slowly from approximately battery voltage to approximately 8 volts (and then increase again)
- End function "03 - output Diagnostic Test Mode (DTM)" by pressing button.
- Select "06 - End Output".
- Switch ignition off.
If specified value is not obtained:
- Connect test box V.A.G 1598/31 to wiring harness connectors, Engine Control Module (ECM) is not connected. Connect Ground (GND) clip at test box to Ground (GND) (not visible in illustration).
CAUTION: To avoid damaging electronic components, set measuring range before connecting test leads and observe all test requirements.
- Check following wiring connection for open circuit and short circuit to Ground (GND) and B+:
- Repair wiring connection if necessary. If no malfunctions are detected:
- Check wiring connection from Coolant Fan Control (FC) Control Module 2 -J671- to harness connector on longmember - arrow -.
If no malfunctions are found in wiring:
- Replace Coolant Fan Control (FC) Control Module 2 -J671-.