Batteries Fans and Ugh


Active member
Mar 8, 2001
Fairfield, IA, USA
2001 TDI Jetta. 130,000 in Iowa with salt on roads in winter. There are many threads about radiator fans and burned wiring and failure etc. But I cannot seem to find what is happening to me.

Last spring the fans would not go off and killed the batterie. I charged the batterie and things seemed to work OK. Then I noticed that the fans did not work. At all. ie no AC. So I was due for timing belt and asked dealer to look at. Dealer explained there was corrosion in the connector that connect to the radiator fan cables under the battery at the lower drivers side corner of the radiator.

A month later I had no fans again. So I got some electrical cleaner and did it again. Looking at the connector I see corrosion. This time the fix seemed to last longer. In fact up until now. However I have another problem. When left at airport parking lot for week or more. Batterie is dead on return. Car is fine when driven every day or two or three. Current drain at batterie is 200 mA. But if I disconnect these two connectors to the radiator fans current drain is 30 mA.

Anyone seen anything like this? Suggested solutions?
Many thanks


Jan 30, 2003
Cbus, Ohio
03 TDI Wagon
Look at the fuses in the box on top of the batttery, the closest one to the passenger side is the one for the fans, It can cometimes blow, or burn around the base, this is the most common problem in fan no-run issues.


Mar 2, 2007
Status Update

Hey Alex P, Do you have a status update. I have a similar issue. If I remove two of the three green fuses I am good, otherwise the battery drains hard (148mA)


Veteran Member
Jun 28, 2003
Central Indiana
'05 GL Passat & '05 GLS Passat & '05 Beetle TDI
Here is a thought on the reason for the battery current drain. The battery is connected directly to fuse S180 and from there to F18 coolant fan control switch and then to the slow speed input to both radiator fans. There is 12 volts applied to pin 2 of the control switch all the time. A continuous application of voltage to a connector that gets salt water in it is a recipe for corrosion. A layer of corrosion in the connector can bridge the gap between pin 2 and pin 1 (to the fans) and cause a continuous low current flow (not enough to rotate the fans).
It will not be enough to simply spray WD40 or something else in or on the connector. If there is a corrosion buildup, you need to remove it with a wire brush or a dental pick. Then a good spray with WD40 or an anti-corrosion coating of some kind might just get rid of the problem. It's important to remove the corrosion because the continual current flow promotes galvanic corrosion which will literally eat the metal connectors up.


Top Post Dawg
Dec 2, 2002
that happened to me this winter had to pull one of the fuses on top of the battery momentaryly to shut off the fans, changed out the coolant temp sensor to the updated one, also the thermo fan switch. Turned out to be the auxilary fan relay :).