Hi everyone.
Hoping for some tips/advice on a problem with cooling fans on my son's Wreg 1.8t GTi . Bought 6 weeks ago, really clean, 93k, drove lovely for first fortnight. Then it had an issue with the cooling fans ever since
I'll try explain in a nutshell.
Fans were pulsing from low to high constantly when the ignition was on, even with engine off. First auto electrician said needed new fcm, new temp sensor, AC pressure switch and then said he thought the ECU was the issue or a wiring faults.
So got car back, tried to get ECU cloned but was told data couldn't be retrieved as it was damaged sobought an immo off ECU and the fault was the same. Changed temp sensor for a proper new VW one. We also fitted a new (aftermarket) fcm and this made the fault worse in the high speed fans were constantly on.
So a 2nd guy came today and spent 6 hours going through things. Eventually determined that a white wire at the fcm had a 12v constant live that was starting the high speed fans. The wiring diagram we had (some kind helper in a Facebook group sent it to me) doesn't have a white wire to the fcm.
Snipping and isolating this wire has stopped the fault, and the low speed fans cut in as they should after we tested it for quite a while .
Anyone any ideas what may be feeding this wire and putting the fans off. Photo attached.
Although it still needs an AC pressure switch we fully disconnected the AC control module and switch and the fault remains. Currently have the existing ECU in place as auto electrician can't find any faults with it and immo off ECU wouldn't perform throttle body adaption.
Thanks in advance. 🤞 And I'm not a mechanic so talk to me like I'm a moron 🤦😆
