Brittany964

My heater / ventilator fan won't turn off even with the ignition switched off. It came on full blast while I was driving on a day which had changed from cool to warm and I'd been adjusting heat setting and fan speed. At the point when I had the fan on full blast I realised that I could no longer adjust it. When I got home I turned off the ignition and left the car, thinking it would cut out when it had cooled down. An hour later it was still running and the battery was virtually drained. The only way to stop it was to pull the fuse. There must be something to try before replacing the control unit. Any suggestions?

Sten

Final stage of thethe heater/blower system - when it goes bad, fan(s) will run all the time.

Brittany964

Thanks for your reply, Barry. Are you saying I need to replace the whole control unit, or is there any way of fixing the final stage?

Computamedic

The final stage driver is a separate part which consists of some driver electronics and a BIG heatsink that sits behind the main electrical panel, next to the firewall. They often come up on eBay (Part no. 964.624.010.02) and a new one will set you back £410 + VAT in the UK.

Regards

Dave

Brittany964

Thanks, Dave. My favourite Porsche specialist says this is almost certainly the problem. He says its unlikely to be the control unit as the fan wouldn't run if this was faulty, whereas I have exactly the opposite problem! I've enquired after the one on eBay and will get it fitted when I visit the UK after the summer. Meanwhile, I'll drive with the sunroof open when its too warm.

Sten

You need to find out what has made it go bad - usually if one of the fans is seized, the excess heat draw through the final stage driver will see off the electronics, so you may need to replace a fan(s) as well. Final stage is easy to change, it sits on the firewall adjacent to the Central Electric Fusebox.

Brittany964

Well, you guys on this forum are certainly very helpful - when I have something really serious go wrong (bound to happen) I'll know exactly where to come - thanks again. Here's the car in question -