setflyn41

Today while idling for about 10-15 minutes my car started to overheat and I immediately shut it off, and checked it out after cooldown and the fans are only coming on when the ac is on,

My ac recently quit working as well, so my on the battery fuse box had previously melted and blew a fuse but I replaced the fuse and all was good, figuring it may be the issue I replaced it with a Volkswagen fuse box from autozone. This fixed my ac again but the fans still only come on when ac is on
before I go throwing parts at it anybody have any tips on how to find out what it is? I don't think it's the fans because they still work just only when the ac is on, and I doubt its the fuse box because that is brand new and all fuses are good,

BryanGuyStatus

I'm interesting in this one as well. My fans will eventually turn on but the other day I was working on a trouble code related to the MAP sensor and I had the engine idling to clear some smoke for not running in four weeks and it heated up to ~270 degrees F and the fans didn't turn on. HOWEVER once I put the car into reverse to give it a test drive they came on and remained on the I returned home and had the car sitting in idle.

OP - is your car modified at all?
I don't recall mine ever over heating at idle until I modified the chip and added the FMIC.

setflyn41

It is not I'm hoping to get it chipped soon but I'm trying to make sure everything is in good shape before I do

setflyn41

I guess I'm going to try the radiator fan switch next ecs says the triangle connector starts in 2003 but mines right on the line a 2002 anyway to tell if it's triangle or square I tried looking but I couldn't tell

Johnny Hallum

So I have a 2003 TT and have the same issue. There are only 3 issues that cause this. First is the temp sensor that screws into the radiator. If that does not close the connection at a certain temp it will not allow the voltage to be relayed to the relay box under battery thus the fans will not come on when car is getting warm. Second is the relay box itself. If it's bad it will not send voltage to the temp sensor allowing it to complete the circuit. Last is fans. That's the easiest to figure out. If you provide 12 v to fan connector and it spins your good. Next check that power is leaving relay box under battery. If you get 12v on outgoing connector it's good too. Last is the temp sensor at radiator. Unplug connection and cross red to red yellow and if fan clicks and comes on shortly after then relay is good and fans are good. Sensor that screws into left side of radiator is bad. That is the most common fault besides relay! Temp fix is cross red with red yellow at connector with paper clip and fan will run constant until you can replace sensor. Your car will stay cool but will overheat fans in really hot weather! This is legit info. Don't listen to other posts

J. Patterson

Great post but one other factor to mention is that the AC makes the fans run too on low speed regardless of coolant temp. A bad fan resistor can disable this. ( as I understand it)
High speed fans do not come on on mine until 100C. Just as the temp gauge moves one notch above center.

eatumup

I had a similar issue last year.. but for me i found my fans were not working while trying to fix my A/C. Theres a fuse box on top of the battery. In it are several fusable links and 3 green blade fuses. Nothing there is labeled. Audi wants to charge 150 bucks for the whole box. My co worker found one on ebay for like 20 bucks (his beetle has the same part).

BUT.. My issue was one of those green fuses. I think they are 20amp fuses. double check. but change those out. for me it was the one closest to the heavy links. Once I changed that everything was good and has been since.



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Parkour Angel

same issue with mine: fans are non-operable and AC does not run. Did exactly what you said, fans run now so no more idle overheating but no luck with AC. Did this fix your AC issue?