No engine cooling fans at low when AC and blower on

2004 Volkswagen Beetle convertible 5 speed
I have no low speed fans when I turn on the ac and blower. To try and resolve the problem I've replaced the following:

FCM (twice), the thermoswitch on the radiator, along with the fusebox over the battery.As well as the fan unit itself. I've also replace the resistor pack and blower with no success.

I've attempted trouble shooting the problem with the instruction in the thread Check your radiator/condenser fan operation NOW. I have signal at the FCM (T14/8) when the ac switch and blower are on but the fans do not turn on. All fuses are good including 5,16, and 25 inside the car.
On T4/1 and T4/3 I have 12 volts. I do not have 12 volts on T4/2 which is required for low speed fans. I took the connector off the thermoswitch and jumper pins 1 and 2, the fans turn on. However when I jumper pins 2 and 3 following the instructions in this thread, I do not get high speed. I took off the connectors for the fans and applied 12v directly, both high and low speeds are working.

Not sure how the lack of high speed would prevent the low speed fans from coming on but this is what I see so far. Also in the pinout for the T4 and T14 connectors for the FCM, it indicates there's another signal required for the low speed, T14/3 for a ground from the ECM when the engines under heavy load. If this is constantly ground would that cause my problem?


I could really use some help here.

Sounds like you have a wiring problem. Last year my compressor would not engage I searched and searched for the problem and finally discovered this at the connector that sits right on top of the starter. As these cars age likely more and more issues like this will crop up.

Tdijarhead said:

Sounds like you have a wiring problem. Last year my compressor would not engage I searched and searched for the problem and finally discovered this at the connector that sits right on top of the starter. As these cars age likely more and more issues like this will crop up.

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Thanks Tdijarhead but I'm not worried about the compressor engaging, I'm just trying to get the fans to turn on with just the ignition key on, the ac switch pressed and the blower on. The AC compressor's down stream from that. If I can just get that functioning, I can stop the car from overheating.

This looks like the FCM I installed is still no functioning properly. I check the 12 volts on pin 2 of the thermoswitch connector located on the radiator and it's present. I also check for 12 volts on pin 1 on the T4 which is the harness on the FCM with only 4 connections, and it's present. However when I check for slow power on pin 2 and 3 on the connector for the thermoswitch with key on, ac on, and blower on and no jumpers there is no power and my test light doesn't light.

I checked the input on T14 pin 8 to verify that the signal from the ac on and blower switch are present at the FCM. When both AC and blower are pressed there's ~ 11 volts present. When either the AC or blower is off,
~0.9 volts are present. I also checked the ground on T14/6 to make sure it was present, it is. I ohm'ed between pin 6 and the engine block and there were zero ohms.

I'm beginning to think I may still have a bad FCM. I purposely purchased a OEM unit to avoid the chinese models but I may have still got a bad one. However before I jump to conclusions, I know there are FCM's with model numbers ending with N and K. I ordered Module #: 1J0919506K, can anyone confirm this is for a 2004 Beetle 2.0 liter?

I could really use some one with experience to confirm I'm moving in the right direction or whether there are other areas I need to check.

UPDATE: I'm having reservations about it being the FCM. I plugged the other FCM I replaced into the two harnesses and retested. It still has the same problem but if I pull and push the T14 harness slowly, I can feel the relay inside the FCM "click" and occasionally the fans do turn on and run. When I turn the key off, the fans will continue to run. This usually indicates something found a path to ground. If I push the T14 connector on fully, the fans will not run. The only condition they run is when I jockey with the connector.

Has anyone seen this behavior? Can the T14 harness be purchased?

When I pull fuse #16, the fans come on at low speed as they should, however when I turn the car off, the fans don't. They continue to run until I pull the T14 harness of the FCM. Fuse #16 controls the power water pump which I don't have and the AC clutch. I tried removing the connector from the clutch but still have the same problem.

There are some junk Chinacool fan controllers out there. I'd only use an OEM one ( you can find them outside of the dealer).

oilhammer said:

There are some junk Chinacool fan controllers out there. I'd only use an OEM one ( you can find them outside of the dealer).

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I don't think it's the FCM. I've replaced it twice already and one with an OEM from Germany and it still happens.

E31 said:

When I pull fuse #16, the fans come on at low speed as they should, however when I turn the car off, the fans don't. They continue to run until I pull the T14 harness of the FCM. Fuse #16 controls the power water pump which I don't have and the AC clutch. I tried removing the connector from the clutch but still have the same problem.

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UPDATE: Found out that if fuse 16 blows it will cause the fans to stay on continuously so this is not my problem.

I have 3 FCM's all failing. I've went thru all the checks in the A4 Coolant Fan testing and here's what's I found. The signal from the AC and blower on T14/8 is there. I see ~11 volts when I measure from T14/8 and the ground at T14/6. What I don't have or feel is the relays inside the FCM turning on. Should I have a relay activate when there is voltage on T14/8?

What page in the Bentley are you looking at?

OK sorry for not updating this sooner been a little busy. So far, along with the parts mentioned prior, I've replaced the blower inside the car behind the glovebox along with the resistor pack underneath it. This is whats used to send the signal to the FCM that the blower's operating properly. Still the same problem. I had checked for the presence of the signal from the blower at the FCM before replacing it and it was there but I figured what the hell, this car's so screwed up it may be something flaky. So I went back to the FCM's. As mentioned in a previous post, I was able to occasionally feel the relays inside one of the FCM engage but drop out. This was with the first FCM I had in the car. I put the car back to together and only drove it when there was no traffic or late at night, thinking the car would overheat. Here's where I made a discovery. I thought what happens if I don't turn the ac on along with the blower. How does the car know when to cut on the fans under this circumstance? The thermoswitch on the radiator because it measures the coolant temperature and when it reaches necessary value, the fans should cut on. So what I did I drove the car around the block a few times to get it to operating temp, then pulled the car into the driveway and let it sit. Sure enough the fans oscillated on and off the way they should. They would come on, run for a few minutes, then cutoff. I let car run for about 45 minutes and it never over heated. To go back, when it did over heat it was when I had one of the cheap chinese FCM's that I only paid $18 for. The one that's currently in the car is the original unit. I sent back the OEM unit cause I assumed it was bad but I never performed this test with it. Currently out of town but when I get home I'll test with the new OEM unit.

So to make a long story short, test the fans both ways, the first with the AC and blower on, but also test to see if they come on when the thermoswitch reaches the operating value. Not sure what this is telling me, is the FCM just partially broke or is the problem downstream from the FCM.