2006 Jetta TDI Cooling fans running non stop when off

[biglsells]

I've had this problem for awhile. It stopped a year ago so I didn't do anything about it but it has resurfaced. Turn the car off in garage and go inside. Go out to grab a pound of beef from the freezer and the fans are spinning away at max speed. Run for about 10 sec, then turn off for 10 seconds, then back on. I now have to pull the fuse powering them under the hood by the battery at night. I bought a whole replacement unit with both new fans, etc. Installed it today, brought it down off the lift, put the fuse in and..... same thing. I can hear an ever so faint clicking (somewhat like the sound of a blinker relay, but softer) then the fans turn on, run, turn off, click click click for 10 seconds, fans back on.

I was really hopeful that would fix it. Next thing I'm testing is the temp sensor on drivers side, radiator. I've read in the forums that could have failed. Unplug and see if condition stays the same. Other than that, what could be it? Can I drive it without the fuse in for now? I'm in Michigan and tonight it's 0 degrees out so it is anything but warm.

Thanks in advance and as always, will close thread with solution.

OK quick edit - I went out to pull wire off sensor, must be on the bottom so will have to wait until I get it on the lift tomorrow. When I put the fuse back in I can hear the clicking before the fans spin up. The clicking sounds like it come from between the engine and the firewall, something back there clicks.

 

[DivineChaos]

Alright so the ecu is telling the fans to turn on. It's not a stuck relay. A temp sensor is erroneous. So you have vag com? I would suspect one of the coolant sensors, or one of the egt sensors.

BUT! Check/clean your grounds and have the battery tested.

 

[biglsells]

Battery is good and my grounds all appear to be just fine. Hooked computer up, temp sensors all read just fine. It's strange because it stopped doing it mid summer and now it's back. Our shop mechanic spent almost all day going through the car trying to figure it out but neither of us could find a reason for it. With this car I'm almost to the point of wiring in a small cutoff switch and being done with it. Took the top fuse box out of the engine bay to check for corrosion but it was fine too.

 

[Rx7145]

I would probably do the cut off switch the humble mechanic on YouTube said (when watching one of his videos) that the fans running on high is indicative of a bad ECU.

 

[BackToFixin]

Coming back to this forum...

Both fans will kick on... then off... then on... until the battery is dead the next morning.

No codes and no blown fuses, just seeing if you found a fix to the problem before I throw my wallet at it.

 

[biglsells]

Sadly, I just ended up selling the car for parts for a grand and moved on.

 

[Rx7145]

Well at least somebody got a good deal.