Cooling fan problems

[deilenberger]

Friend who is a mechanic has a customers '05 CS in. The problem is the primary cooling fan seems to have developed a mind of it's own.

Symptoms:

1. Never shuts off (without fuse removal)

2. Turns on as soon as the ignition is turned on - even with dead cold engine

3. Runs at what sounds like full speed (think jet engine turbine noise..)

Questions:

1. Anyone had this problem? If so - the fix was?

2. How are the fans triggered? From descriptions it appears to be controlled through the motronic, but the circuit diagrams show a fan control unit - without any inputs from anything.

3. Anyone know where the fan control unit physically is?

4. Is there a speed control module on the fan itself?

TIA!

[working4it]

I thought I would attach this for you...I didn't have time to review it. I will look for it later....

ELECTRICAL COMPONENT 2.pdf

[deilenberger]

Thanks! We had this - and strangely enough, it doesn't list the fan control unit (even though circuit diagrams show it..) Go figure..

[Loren]

Click to enlarge...

[wvicary]

The coolant temp sensor can also cause this fault.

[deilenberger]

Loren, thanks for the diagram, I passed it to my mechanic.

Wvicary - he tested the fan by unplugging it from the car, then hooking up a battery to the ground and power feed wires. No trigger voltage - the fan started up and eventually reached full speed. His feeling is the speed control module on the fan has passed on and it needs a new fan.

[normandinjf]

I'm having the same problem! Any solutions?

[Loren]

I'm having the same problem! Any solutions?

Has someone checked the car for faults with a PIWIS tester?

[deilenberger]

I'm having the same problem! Any solutions?

The replacement fan arrived today (> $500) - will probably be installed tomorrow. And no - the independent doesn't have a PIWIS, and since my Durametric is VIN limited, I wasn't going to plug it in..

The size of the wiring and power connector for the fan is simply amazing - huge plug. And there is lots of electronics on the front of the fan motor.. be interesting to dissect the old one once it's replaced to see if something obvious has failed.

BTW - the old fan and the new fan both have 4 wires coming from them (and a 4 wire plug).. it isn't clear by the diagram above if it's showing 4 or 5 wires.. the two wires going to the 2nd connector appear to be alternative wires (one for V8 and one for V6).. so not sure how accurate that diagram is.

Edited October 5, 2011 by deilenberger

[deilenberger]

Just an update.. (since people rarely remember to do that..)

A new fan fixed it. Tried to disassemble the old one to see what cooked, but it's sealed up very nicely. Lots of electrolysis noted around where the wiring goes into the electronic box on the fan motor. I guess putting the connector at the top of the motor seemed a good idea to someone..

[JSP]

My 2008 turbo has just developed the same problem. The radiator fan turns on full speed when the ignition is turned on (cold engine) and runs continuously when the engine is running and for about 30 seconds after the engine is off. Thank you for the resolution and update Don!!

[JSP]

Ditto for me, also replaced the fan and it fixed the problem, there was a crack in the connector on the control unit on the back of the fan motor where the wiring harness enters it. Green oxidation was clearly visible once the fan assembly was removed from the vehicle. The quality of this expensive part is disappointing, shame on Bosch, V.W. and Porsche for not making this better. I have much older American and Japanese cars with more mileage with dual electric cooling fans that have not had any problems with the fans. The part number is 0130706202 by Bosch approx. CAD$520.00 not cheap!