Radiator Fans Turn on While Car is Parked and Off

I have been needing to make this post for a while, but having a baby kind of got in the way of my automotive projects.

My wife's 2005.5 Jetta TDI has been sitting up with the battery disconnected because the radiator fans keep coming on for no apparent reason in the middle of the night. The car will behave fine for a while after you dive it, and then after it has been shut off for an hour or two the fans just turn on and ramp up to full speed for about a minute and then turn off. This continues until the battery is too low for the ECU to even think of powering on.

No codes on VCDS.

I wife would really like her car back.

Looks like your fan controller is deffective.
It is located inside one of the fans.

So you must replace the fan to fix this.

Check the fuse on top of the battery; I don't know which one. On my MKIV Golf, there is a fuse on the side panel inside for the A/C, and if that fuse is bad or removed the fans keep running. This may or not apply to the BRM.

I replaced the big fan.

That didn't fix it. It still starts up the fans on its own after sitting for a while.

It's perfectly normal for the fans to come on or off while the engine or AC is or recently was running. That being said if it is draining your battery you have a bad fan control module. The module is located in the big fan. When I replaced this in my car it fixed the issue. Unless it is draining your battery it's not normal.

Frame, the car can be sitting for days without being driven and the fans just turn on for no reason. It has a brand new fan control module and big fan. That is not the issue.

So... It turns out that the fans will shut down if I pull the 40 amp fuse for "right side lighting" a.k.a. J519 "vehicle electrical system control module"

The fans will run and behave normal when you start the car without the 40 amp "right side lighting" fuse.

Any update on this, I have a gasser 2005.5 MK5 Jetta that is doing the exact same thing, I also replaced the fan control module and large fan and it is still doing it. Also no VCDS codes.