Fans playing up

[Richierich84]

Hi having another problem with my 1999 s3
when I put the ignition on the fans kick in straight away! there sort of pulsating on and off. has any1 got any ideas why it might be doing this? also the smaller 1 of the 2 fans is making a racket due to the bearings gone inside. can I just disconnect it and run on the single fan or will it overheat ? Cheers

 

[Scullies]

mines doing the same now. Just out of the blue.
Turn key on, engine off, both fans turn on and off continuously. Coolant temperature sits at 88 while driving. No issues while driving when I come to a stop and wait at the traffic lights, the engine starts to hunt as the fans turn on and off. Rpm dips low then engine recovers and rpm just up to 1200 then down to 800 when fans turn off. As soon as the fans come on again the rpm dips and so on and so on.

Anyone else had this happened?

 

[Scullies]

Ok, so I unplugged the fan control unit ( relay box ) and the plug for the temp sensor on the radiator, all looked clean but I went ahead and sprayed contact cleaner on the plugs, sensor and relay. Let it dry off and plugged them all back together. Seems to have solved the problem.
My guess is dodgy wiring somewhere, dodgy radiator sensor or fan control unit.

 

[Scullies]

Update,
After a few days, the fans started doing their own on/off story. So I replaced the temp sensor in the radiator and replaced the control unit. Still the same on/off story.
Guess its time to hunt down electrical faults.