MK5 GOLF GT TDI: AIR CON FAN PULSING AT HIGH SPEED

[chakatee]

Hope someone can help with this. I believe it could be a common fault with MK5 Golf's.

My Golf is a Mk5, GT TDi, 2004.
I recently noticed a very loud noise coming from the radiator fan when I had only switched the engine on.
I have the digital climatronic air con. I have two radiator fans.

After having a look, I got the following result:

1.turned engine on.
2.turned aircon on.
3.made sure ECON is "OFF".
4.The fans do nothing then, after about 20 seconds, the one on the right-hand side as you look down (passenger side) runs very fast. This fan then
  stops after a minute or 2, then starts running again at high speed.
5. The fan only runs at high speed like this when the air con is switched on. As soon as I switch the air con off, the fan stops.


Can anyone please advise or has any experience of this. Unfortunately, I don't know much about these things so I am reliant on the advice online to help me. The dealer prices for diagnosis and repair is normally very expensive.

From what I have read online so far is that a faulty fan controller or a resister fault could be the problem.

Any advice would be greatly appreciated.

Thanks,

[john87]

Isn't the fan supposed to cycle on/off at high speed mode to help cool the air con heat exchanger (condenser) ?

Can't say I use the AC very much so haven't heard it in my Golf, although my Civic used to do this and it was the norm in Hondas 

[chakatee]

A VW garage advised today that he is pretty sure that both fans should switch on at slow speed as soon as the AC is switched on? It shouldn't just be one fan.
He said, probably the smaller fan is defective and has seen some similiar faults.

If the small fan is defective, does the large fan detect this through the control unit it has and run at higher speed to compensate?
Would replacing the smaller fan fix the fault?
Are there other things to test such as the engine bay fuse box (what would I look out for and where) and damaged wiring would I be looking for (again what and where).
Much appreciated.

Cheers,

[doylebros]

If I was you I would check this list:-

http://www.mk5golfgti.co.uk/forum/index.php/topic,120.0.html

See if anyone is close to you to perform a full VCDS scan and an output test on the address 08 HVAC system - this will allow testing of both fans and other system components!