You could just temporarily hardwire them to a switch(maybe even underhood) for the DE, and leave them on while on the track. Mark Kibort runs his that way and it seems to work out fine. If you can't get it fixed right for the DE, that would keep you from missing the event due to a silly control issue...

 

Dennis, I tried to trace the wires, but they disapear into a big harness running towards the firewall on the passenger side.
Dave, great idea, I guess that's what I'll have to do. But I wonder where to get the power. I guess from the "jumpstart" connector and simply put a switch and fuse inline...

I will try to clean the fuse contacts and I guess there are two relays involved somewhere, maybe that could be the culprit. Anyone knows which relays?

Thanks,

 

I did a search--this might help:

Do the battery terminal cleaning, especially the positive cable and those red aux connections from the battery positive cable. Each fan has a dedicated power lead from the battery, each through a dedicated fuse (28 and 29), to that output module. Possible resistance poiints are the fuse/fuse holder, and the connections at the battery itself.

Had a guest car a couple years ago here that had loose fan wire connections at the battery, causing the fans to run only occasionally. Clean/tighten the wires back there, ran fine.

Also be aware that the hood switch needs to be depressed when testing the fans with the hood open. You can 'force' the controllers to high-speed by connecting the two wires at the thermo-switch on top of the intake manifold. Siimulates a hot-soak condition. Handy when troubleshooting the fans.
__________________
Bob Fuelleman


'89 S4 Auto, black

 

Thanks Bob, I will clean those connections right away, even thogh things look spotless back there. I would still think there is a relay somewhere, no?

To my understanding the fans should run regardless of hood switch if the AC is engaged.

 

I'm a little late to this thread, but I wanted to warn everyone about letting these engines overheat. My '79 came to me with a seized water pump and had been driven by someone (either PO or shipping company) such that there was NO water in the expansion tank when I got the car. Engine is now pulled for blown head gasket and it is not certain that this car will ever run again.

 

Sab,

There are two control boxes for the fans on later cars. One is a small silver box mounted under the cover between the passenger seat and the doorsill. One is a black box with heat sink fins, mounted just behind the headlight bar on the same piece of metal that holds the hood latch, toward the passenger side. You might want to check the connections on both of these boxes as well. IIRC there is a troubleshooting guide in the WSM and/or tech docs on CD.

 

There is no relay beyond the FET amplifir module on the front apron.

The connections on the victim car --looked-- fine. On the battery terminal, the clamp bolt has 8mm threads one side through the battery connector, 6mm stud the other way for the accessory and fan leads. Pull the bolt from the clamp and the wires from the stud, and do a little wire brush work to get the lead part of the clamp looking new again. Not grey-new, shiny new. The connections to the fans are ring lugs with tin plating, so the stud/bolt needs to be shiny new on both ends and the ring lugs need to be shiny before reassembly. I added a stainless locknut to replace the little 6mm/10mm hex on the aux lead end of the bolt. Snug it all up, and add a coating of Vaseline, or you can use some dielectric grease if you wannt to use something expensive to feel good... The Vaseline will do the job fine though.

Theo Jenniksens (sp?) has a great fixit instruction for the front fan 'amplifier' module that covers replacing the FET elements with parts you might find at a Radio Shack store. If you find that the problem is that front module, and you have a soldering iron and some patience, you might want to try that fix.

Others have reported problems where the fuses fit in the fuse panel. High load plus some resistance = heat, and that can cause panel problems that might not show up immediately. A finger test for HOT around 28/29 fuses isn't too tough. The terminals in the panel can be removed to clean/buff up, or you can buy the brass/copper fuse terminal inserts if you shop carefully at the VW or 944 counters at your dealer.

To test for overheating at either the fan motor, the module or the fuse panel, you can force the fans to run by connecting the two wires that attach to the temp switch in the top of the intake manifold. Simulates a hot-soak condition, runs the fans. Put the battery maintainer on for this exercise. If it's going to fail when you drive it, this should duplicate all but the fan motor heat absorbtion as you troubleshoot.

The easiest troubleshooting for the modules is to swap them with known good and see if the problem goes away. The WSM procedure is less than perfect, but is a good start.


HTH!

 

Thanks for all the suggestions, I found the problem. I swapped the fan speed controller located under the hood from another car and botth fans worked fine on mine and only one on the other car after the swap.
So I need a new or used one fast. Looks like they are $328 new and $150 used.

Do these things brake often or is it pretty safe to buy a used one?

Thanks and regards,

 

Glad the controler swapped worked!
Heck id just get used. Look how long the original lasted!

Nice to meet you guys Friday