Weird One - Fans on Audi A3 8l

[leventis]

Hey Guys,

Have an Audi A3 8L. The problem I have is with the fans. Before you tell me to read the threads as been covered many times. The problem is when you turn the car to accessories (ignition on) the fans start pulsing. Now I dont think they should be doing this. Also when the car is turned on the fans are pulsing.

Whats has been done:

- Checked all fuses, even the ones on top of battery
- Bypassed Low speed fans with resistors (been covered a 1000 times in other posts)
- Checked the radiator sensor and bypassed - low speeds work fine without car on. As soon as ignition switch on and wires bridged the fans pulse and then will speed up to high speed.
- Have replaced fan control module
- Temperature sensor has been replaced.


So basically low speeds work and high speed however fans still pulsing. Have also replaced both fans as my main larger fan eventually failed.

Anyone have any ideas, have not been able to search much on the net.

Thanks
Chris

[JustCruisn]

This vid covers how to test the fan circuit itself.
vw Golf mk4 fan switch check climatronic fan check guide - YouTube (http://www.youtube.com/watch?v=Af-jT9cAioM)

With IGN off you can get low speed, with IGN on you can get High speed.
If this test works OK your fans and the last part of the circuit is OK.
If they pulse when in high speed mode you may have an issue with the fan itself.
What is the frequency of the pulsing ? High for how long ? low for how long?

[leventis]

Yes I know that video. As stated high and low have been tested on the fans themselves. Low speed works fine. When you put the ignition on without bridging the highs the fans pulse.

[007]

That is odd. Sounds like a dodgy fan control module. Have you seen this?

http://pics.tdiclub.com/data/516/A4_Coolant_Fan_testing_Rev_7.pdf (Testing Fans). A process of elimination, but a PITA. Good luck with it