Hey, I apologize right now for failing high school electronics class lol. Here's the deal, my fan control module fried from coolant exposure due to a bad oring on the res cap. Anyways, fans were stuck on and module was smoking just waiting to catch a blaze.
I had to cut the FCM from the cars electrical harness. Now, I couldn't find a replacement in the junk yards and can't afford $175 relay when I know I can make this work the same for a hell of a lot cheaper.
Currently, I have the low speed fan wired to a 4-pin relay triggered off the temp switch on the radiator.
I'm usin the OEM 3-speed cooling fan, it's already got resistors built in to it to control speeds, it just waits for the FCM to tell it which speed.
I'm getting my AC repaired this week and I'll need to get the high speed fan working accordingly. My idea was to use the AC compressor hot (+) feed and splice it to another relay to activate the high speed fan circuit.
My concerns, is runnin the fan at full speed the whole time I drive it with AC on, and feeding the fans low and high speed circuits at the same time.
I wanted to use a second relay for the high speed fan triggered from the AC button/compressor circuit, but disengage the low speed relay (interrupt ground?)
Can anybody help me out?
Try this:-
jetta_fan.png
Notes, depending on load, you may need 70-80 amp relays rather than the standard 30-40 amps, check your fan fuses.
Relay B the diagram assumes the thermal switch on your rad goes to ground NEG (-).
If POS (+) connect thermal switch lead to 86 and ground 85.
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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.
Thank you so much Howie, saved the day. And saved me $200 for not having to fork out for a new FCM ✌️
