[sandy the saab]

I had a faulty fan which I have now replaced. Unfortunately it still doesn't work. I have replaced the thermo-switch on the radiator and checked for the 12v feed to it. Swapped the relay with the one for the headlights (it has the same number on it). Checked the fan by applying 12v direct to it and checked for 12v at the input to the 30A fuse. It says in the manual to put a loop on at the thermo switch and the fan should come on. It doesn't! Have checked the wiring from the thermo switch to its' connection into the loom. Anyone got any ideas where I should go next? Any pointers will be gratefully received

 

[Mark B]

The thermoswitch turns on the fan by means of the relay, as does the air con pressure switch. The blue wire between the switch and the relay has a habit of breaking or corroding somewhere inconvenient.

See this post.

 

[badman]

There are 2 or 3 wires (model dependent) connected to the thermo switch via a block connector (close to the switch).

It is extremely common for the blue wire to be corroded or in poor condition somewhere between the block connector and the relay box. I don't know how closely you inspected your connector when replacing the switch, but even if it appears clean and in-order, the chances are that the blue wire has failed elsewhere)

On my 9000, I pulled the block connector apart and found that the terminal to which the blue wire was connected had corroded away completely. I stripped the wires back to good metal and tried to bridge the connection block, but no avail – I guess it was shot somewhere else too.

To test this wire on your car you can do the following: remove the relay, then bridge the uppermost and lowermost terminals with a piece of wire (insulated from your fingers!). If the fan kicks in, then cause of the problem is almost certainly this wire between switch and relay box.

In the end (from the advice of many people here) I ran a new wire directly from these relay pins to the thermo-switch….. bingo, fan cuts in and out as it should.

NOTE:- My car has a 2 wire thermo switch. I have no experience of 3 wire setups, and/or if the relay is different (i.e. you may need to test different pins???) I’m sure someone else can help here….

 

[badman]

oh... too slow, Mark B beat me to it!

 

[sandy the saab]

Thanks very much for your advice guys. I will try to bridge the relay connectors to see if that works. If it does, I will run a new wire from the thermo switch direct to the relay socket. Is the wire blue at that end too? Does anyone know where I should expect to measure 12v on the relay socket with a short across the thermo switch connectors?

 

[Norsjo]

Hi,
Fixed the same problem at the weekend, the blue wire had previously been fixed and it was clear that it had come loose again.
That didn't fix it, it was just luck that I noticed on the other side (rad side) of the connecting block the black wire "stud" had come out a few mm from the connecting block, worth checking or doing away with the block entirely.
Mvh