Cooling fans inop

Michael Owner/Technician Quakertown, Pennsylvania Posted   Latest   Edited  
Question
Electrical
2004 Volkswagen Beetle Cabrio 2.0L 4-spd

Vehicle is overheating but only at idle. Verified no cooling fan operation when the engine reaches operating temperature when they should come on (195 degrees) but I'm relying on my thermal imager with this because of not being able to find ECT temp in my Verus Edge. At the 3 wire thermal switch I have B+ at the red terminal and at the controller KOEO. When I jumper red to red/wht the fan should run but it does not. I manually put power to the fans with a power probe and they run but briefly. It blows the internal fuse in the power probe after about 2 seconds. How can I verify that the fan control module is trying to command the fans on? Would I be able to see this command take place with a lab scope probed at the wire that goes to the fa control module? 

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Alan Mechanic
Raleigh, North Carolina
Alan Default
 

Verify the supply voltage under load. The fusebox above the battery will melt at the contacts. Remove the blade fuse to check for burnt spots. Does the compressor clutch work?

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Michael Owner/Technician
Quakertown, Pennsylvania
Michael Default
 

No, it does not

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

as to finding the ECT in data, switch to OBD2, instead of VW.

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Michael Owner/Technician
Quakertown, Pennsylvania
Michael Default
 

Thank you!

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Robert Owner/Technician
Westerly, Rhode Island
Robert Default
 

the fan motors them self are a common problem. I would unplug the fan motors and with some jumper wires see If the fan works.

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Michael Owner/Technician
Quakertown, Pennsylvania
Michael Default
 

I ended up piercing the fan motor wiring just because disconnecting wasn't easily accessible and they ran for like 2 secs and blew the internal fuse in the power probe.

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Daniel Owner/Technician
Ingleside, Texas
Daniel Default
 

...Hey Geoff....Hobbs made it over here...good to see ya's...Dan H.

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

Good to see you too. :-)

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Tom Mobile Technician
Chicago, Illinois
Tom Default
 

According to to the diagram you posted the cooling fans should run on low when you jump red to red/wht at the thermo switch. Don't need the cooling fan module for that.

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Sean Technician
Cincinnati, Ohio
Sean Default
 

The main fuse in the battery fuse box, should be a bolt in style fuse I made an j fuse adapter to bolt in place, so I could do an amp and voltage test at. But typically it's the fans, and if my fuse area checks out I scope the control wire from the fan module it's a pwm signal, if the fuse is blown, I have found it will do a 2 sec rapid pulse every like 5 sec to keep trying to turn on the fans.

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Michael Owner/Technician
Quakertown, Pennsylvania
Michael Default
 

Sean, thanks! Can you elaborate on how you made the fuse adapter?

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Sean Technician
Cincinnati, Ohio
Sean Default
 

2 eyelets to bolt too where the fuse bolts then I take the blade butt connectors and wire to eyelets, install blades to 40 amp j fuse. (Or respected size)

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Edwin Technician
Ogden, Utah
Edwin Default
 

Install a halogen bulb in place of the fans.

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Randy Diagnostician
Glendora, California
Randy Default
 

Fan control module very common problem

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Keith Owner/Technician
Etna, Wyoming
Keith Default
 

I have had many euro fans cause this, where the fan will blow the j case fuse, but with a power probe will spin then short out your tool. i have just done this exact thing on a mini cooper, new fan solves it

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Randy Diagnostician
Glendora, California
Randy Default
 

Ok current ramp fan and see what you have

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