Fans help still needed

[Chef_32]

Hi,

So I've been having ongoing problems with my fans running without even starting the car. Basically I go to the car, open the door, close the door, after about 10 seconds the fans kick on full speed and don't stop until I open and close the door again. All this happens without me doing anything with the key. Even happens when I disarm/arm the car before and after.

FYI, i've replaced Fans, Fan Control Module, Relay, Coolant Temp Sensor (the one behind the engine), I've recently done the timing belt, pump, tstat, but the problem existed before this too

Any ideas on whats kicking the fans on?

2.0 Auto Quattro btw.

[shahk62]

Is there any water inside the ecu cover


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[Chef_32]

No Water in the Ecu at all

[Okedokey]

Check each component on this diagram, fuses, continuity and voltages. Only way to check. If you have a VCDS, then use that and see what codes it throws.

[Chef_32]

I've checked 2 and 4 from the Control Module. I know 2 is working because the relay kicks on and off when the car is running. I just need to check 3 but I'm sure the ECU is telling the FCM to run. I'll double check but any other ideas?

[Okedokey]

Check what voltage you have at S4 with the key on and off, and also T17d to ensure you have voltages that correspond with the relay conditions. 4 should have 12V+ all the time and 1 should be ground. After that (all being well, you're needing to check continuity between 3 and the ECM.

[Chef_32]

1 grounds fine, no resistance
4 gets full time 12.5v

S4 gets 12v on opening door.

Reading the diagram, I'm not sure whether to check both relays or just J757 since both seem to be there however J757 does have a green wire going into T17d/17

When I open the door, Relay 2 (J271) clicks on with 12v and Relay 3 (J757) gets power with no click but only at 3.3v. After 2-3 seconds relay 2 clicks off and both lose power. When they have power for those 2-3 seconds the fans will come up then go off, this only happens after the car has fully switched off (dash lights go out,etc.)

Sometimes the fans come on and don't turn off. When this happens even pulling the relays don't turn it off. There seems to be some current still coming through 2 to the FCM of about 0.03V. Also the line 3 gets power of .055 to 0.033 when the fans are on after the relays shut off

At the moment I'm struggling to replicate the issue perhaps because I switched around the fuse but I suspect there is a short somewhere. I've been able to trace wires from T17d back to the relays and ECM, now i need to get under the dash to trace the wires back to the fuses and to the fan controller.

[Danaldson]

Its the white relay ( one closest to the front of the car if i remember correctly) underneath the ecu. Just went through this. 40$ part.

Caused from water getting into the ecu cover.

Sometimes it can dry and be fine.

[Chef_32]

I've changed and checked the forward 614 relay and its fine from what I can tell.

[Okedokey]

Replace both, you can get them much cheaper, you simply need a relay that is rated to the same power, 12V and with the same internal config and package. I got mine for like $8 each. Replace both at this stage. If either are failing or one is failing and the other not, you will probably get a fail safe on condition.

[Chef_32]

yeah fair enough, i'll order a couple more and switch them out...

Need to find someone with VCDS in houston to help me out