Hey Woodchuck..

Sorry to here that but I have to agree with the dealer. What I think happens is one fan low speed goes but you don't notice the engine running a bit warmer. It's not until the other fan goes then all your problems start. As for the voltage it would be hard to measure since the resistor is internal to the fans. I would ask the dealer to request the VW rep to call you and see if he will help out($$$) for the repair since the cars only 2 years old and 34k! Insist on talking to the rep directly and see what he says! BTW, where do you live, state and city is fine.

San Jose, Ca

I called the VW 800 822-8987 number, 'customer service' ?? ... maybe the 1st fan failed at 9600 miles when the car was taken in and a fan problem noted at that time??

do you have any idea what the voltages are to the fan? 12V for sure, high speed I imagine, and a lower voltage, maybe 6V (but I'd like to know here).. for the slow speed.

Thanks

Scott

I think what Woodchuck was getting at is that you do not actually provide two different voltages to the fan for the different speeds, rather the voltage is reduced by using a series resistor built into the fan unit when the fan is running at low speed.

These series resistors get quite hot, and it is not uncommon for them to break. When they do, you are stuck with a fan that runs on high speed only. It can be fixed fairly easily by adding an external resistor. The fan has three wires going to it: Ground, which goes to one side of the fan motor, battery voltage for low speed, which goes to the other side of the fan motor through a resistor and finally battery voltage for high speed which goes to the ungrounded side of the fan motor, bypassing the series resistor.

If the internal resistor is broken, connect the low-fan-speed wire from the car through a resistor to the high-fan-speed wire. The challenge becomes finding the right resistor value. You could measure a known good fan unit (resistance between the two non-grounded inputs) or perhaps it says in the shop manual for your car. Make sure the resistor is rated at sufficiently high power.

Scott C wrote:

Yep, but personally I prefer to fix things the correct way but just replacing the faulty fan!

I think I am having the same problem here (91 Jetta, WVW . . .). Let me ask you this. If the fan has two speeds, are both utilizied when the engine is off or is just the one speed activated (the slower one, I assume).

The reason I ask is that sometimes when I get home and turn off the engine, the fan will kick in for a while, drawing heat out as it should. The coolant level in the reservoir remains steady. Then the fan turns off (and I assume coolant temp has been reduced appropriately) but the level in the reservoir starts to creep up bit by bit. Eventually, some coolant leaks out (steaming).

Why is this happening? Seems that the fan should have stayed on longer. Should it have dropped to the lower speed? Does it only turn at one speed when the engine is off? My mechanic said that when the engine is off, the fan will only turn at the lower speed (to conserve the battery), but I am not convinced of this.

The fan control system is fairly complex on many A2 generation cars. You have the high and low fan speeds during normal operation, you have the after-run based on coolant temperature (low speed only, I believe) and you have the after-run based on engine compartment temperature and time (also only low speed).

I remember see>

If coolant is coming out the cap then I would replace the cap. Been awhile but most 91's also had afterun fan system that could run the fan on low for about 12 minutes max depending on under hood temperatures.

Those darn O-rings. I pulled the cap off and looked inside. About 1/3 of the O-ring had slid up into the bottom thread. It seems that I was not getting a complete seal, thus could not hold fluid in system (ie, a leak in my pressure cooker). I reseated the O-ring and placed the cap back on. Ran the engine for a while, fan came on as usual, turned engine off, fan kept going, then stopped. The coolant in the resevoir held solid. I can only assume that I have re-achieved complete pressure seal and thus preventing the expansion of fluid that has been plaguing me. I was really perplexed why the coolant level would rise so much (I have been watching my '97 after arriving home and the level is always constant).

As a follow up, I will monitor things and replace the cap if necessary. My only concern now is that the O-ring has been damaged; visually, it looked intact. Can just this be replaced? Is there any other aspect of the cap that can deteriorate thus requiring replacement?

Great.. this is what I expected and appreciate the clarification. Both my resistors must have fried.. and I'm surprised VW customer service AND the dealer don't see this as a 'problem'.. but official word is that with 36K miles, they will not cover the repair.

I have many 5-10-20- up to 100 watt resistors and will play with this a bit.

Woodchuck - I have a VW manual, but any hints to getting the fans out easily???

thanks

sc