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I fix it, she drives it..
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Discussion Starter #1
My wife has a 2006 beetle with the 2.5l. The radiator coolant fan (single fan with integrated fan control module) runs on high constantly. It doesn't even need to be started, just turn the key to the run position and the fan starts running fast after 10 seconds.

I get a P0480-004 code, coolant fan control circuit 1: electrical malfunction - no signal / communication.

I bought a supposedly tested fan from a junkyard, but it acts the same. Either the replacement is bad or I have something else wrong. I told them I would try troubleshoot more before returning it.

I built a breakout cable with connectors from a junkyard and measured the signals with my scope. This fan has a 4 pin oval connector - 12v power, GND and 2 smaller control wires. It appears the one wire must come from a controller in the car as when the key is turned to run it goes up to close to 12v with a square wave pulse train on it. When I disconnect it from the module the fan stops. When reconnected, the fan starts after 10 seconds.

The other small wire appears to be driven by the fan control module directly attached to the fan and part of the fan motor assembly. When the fan is energized this signal goes to about 12v and then drops in voltage a volt or 2 as the fan winds up in speed.

I found online that the coolant temp sensor affects the fan control, so I bought a new one and plugged it in, but that had no change in fan operation. Still runs full speed with key in run.

I found online that the intake air temp sensor also plays a part in fan speed. I used vcds to get a readout of intake air temp and it was off, but not crazy. It was reading 35 degrees Celsius (95 degrees Fahrenheit) when actual air temp was about 15 degrees Celsius (60 degrees Fahrenheit).

Does anyone know what the signals to / from the fan control module should be with the key in run? How about when the fan is running? Any suggestions as to how I can debug this or prove the used replacement fan is good or bad?

Thanks!
 

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I fix it, she drives it..
Joined
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5 Posts
Discussion Starter #2
I've got a couple new clues today. I went back to the junkyard and exchanged the fan I bought for another one. I hooked it up, and at first it seemed to act just like my old one and the first one from the junkyard. I realized though that when I start the engine with this one attached after 10 seconds it runs up fast (like my original), but a little bit later (maybe 30 seconds, I didn't time it) it appears to slow down for a few seconds and then goes back up again. It cycles like that one more time in another 30 seconds or so.

I had the heat / AC turned off, temp set to warm and air set to come out floor or dash vents and noticed my AC compressor clutch was engaged and spinning. Does the AC compressor in these run all the time or should it be off with the heater controls set as described? Could this be related to fan running on high all the time?


Thanks!
 
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