Technical Heater Fan - Stuck on Fast Blow (Ign off !!)

Currently reading:
Technical Heater Fan - Stuck on Fast Blow (Ign off !!)


New member
Jul 24, 2005
As Title.

Wife came home, turned off the car and the heater fan came on fast, and will not go off.

Have removed Fuse No.5 under the steering wheel, and it is now off (for good !), but anyone any idea what may be the cause/remedy ?

I know a lot of stuff goes via the ignition barrel switch, so maybe thought it might have got stuck in there ?



(Marea Weekend JTD HLX130)
Looking at the wiring diagram, the ignition switch only energises the associated relay so if there was a problem with the ignition switch the rest of the fan controls would work normally, i.e. you would be able to turn the fan through the various speed settings.
From the relay power goes to the fan speed control which dictates which of the speed resistors is used, then on to the fan.
As your fan is staying on high speed I would suspect a wiring short somewhere which is providing 12v straight to the fan motor. May be a real pig to find, good luck:)
It seems to be the Climate Control taking over - Fuse 5 is for that, Fuse 9 is for the heater fan motor.

Realised this as the Outside Temp sensor is not working since fuse pulled.

Possible faulty sensor somwhere ?? - don't know why it keep running when car switched off though !

Pull the relay, if the fan keeps running that will rule out problems with the ignition switch and relay and virtually prove there is a short somewhere between a permanent 12v source and your fan motor.
Pulling the heater fan fuse doesn't stop it, but pulling the climate fuse does. Noticed that when the fuse is back in (and the fan is running) the Outside Temp sensor is not working when pressing the button inside. Possible sensor/connection fault - making the climate control/heating go wonky ?

If the Climate fuse is out, then the heater stays on the temperature it was set to when it was in (thought it might be wire controlled - but it's never that easy) :)

If the relays not faulty, then I would guess that someone may have messed with the electrics at some point.
I always thought that once ignition is turned off the electrics are effectively isolated.
I did have an old Saab 900 many years ago that could be started by shorting the radio wires out, strange but true.
If powering down the climate control circuit stops the fan that would suggest that there may be a short between the climate control circuit and the heater fan, especially if pulling the fuse controlling the fan does not stop it.

You need to start looking at the wiring, especially where it goes through or sits against any surface, corner or component that might chafe through the insulation. Trouble is of course most of the wiring for the heater/fan etc is well buried. If you are not up to speed on electrics I would suggest you take it to a decent auto electrician. It may very well be that he will have come across this problem before and know where to look.