Rad Fans

[S3 AKR]

How can I test that they work. Being a diesel I can't seem to get the temp over 90c but the fans are not kicking in. The aircon rad fan is also not spinning which is probably the reason my climate aint working too!

Any help appreciated.

 

[Muttley]

If you can't get the temperature up to 90°C then the radiator fans are the least of your problems. 10 minutes open road driving should get you up to temperature, or just go out in the middle of the day . .

Possibly thermostat stuck open? Or water pump?

The radiator fans are triggered by a thermoswitch in the radiator itself. You can remove this and stick it in a saucepan on the stove, with a thermometer, and check that it performs as specified:

1st speed
on: 92...97 °C
off: 84...91°C
2nd speed
on: 99...105 °C
off: 91...98 °C


There is no separate "aircon rad fan". Both fans should run at low speed when the air cooling compressor is engaged ("snowflake"). There is a separate fan control module under the battery tray.

 

[Cyclone]

Am assuming the diesel is the same as the LCR, but by bridging contacts on the thermo swith connector on the radiator you can test both fan speeds.

See below from http://uk-mkvs.net/forums/p/59897/449470.aspx#449470

Caution keep hands etc away from the fans during this test as they are expected to run:

Reconnect both fan connectors, if still disconnected, and disconnect the triangular 3 pin connector from the radiator fan thermo switch.
Bridge contact 1 and contact 2 with a short piece of wire, the fans should run at low speed.
Switch on ignition, bridge contact 2 and contact 3 with a short piece of wire, the fans should run at high speed.
Switch off ignition, reconnect thermo switch connector.

To identify the connector pin numbers, hold the connector facing you with connector latching mechanism at 2 o'clock, pin1 is then at 12 o'clock, pin 2 at 4 o'clock and pin 3 at 8 o'clock.

 

[S3 AKR]

Cyclone - 'kin hell of a lengthy informative thread you linked to there mate! I'll be doing all that tomorrow to check it in full. Big thanks!!

Muttley - again, big thanks. I have run the car on idle for ages without any fan kicking in (aircon set to LO and in auto, snowflake on) and with vag-com plugged in monitoring coolant temp in a number of places and nothing above 90c. Also used the built in "output test" funcions on engine and HVAC modules with no fans spinning up at all.

Today, I ordered a new fan controller (before your responses) and I'll fit that after the tests you have both recommended.

Again - thanks for taking the time to respond guys. Its much appreciated.


Andy.

 

[Muttley]

Idling will never get the coolant up to temperature. Diesels are more efficient than petrol engines, which means more of the bang gets turned into torque, and less is thrown away as heat.

When idling, diesels are running incredibly lean, using practically no fuel and generating very little heat. Take it for a run.

 

[S3 AKR]

Seems to be the fan controller as I can't get them to spin up. Should have the new one Monday so hopefully switching that over should give me my climate control back!