Radiator fan not going off

[Madgooner23]

This seems to be an annual problem for me. Have a 1.9 diesel, first run out in the sun this weekend, fan won’t go off. Changed the thermo switch, no joy. Annoyingly I have to take off the battery in order to stop the fan. Any ideas anyone?

[Forden341]

Sounds like the fan relay may be sticking on perhaps. Does it stay on even if you unplug the new thermostatic switch in the radiator?

[Madgooner23]

Yes it does. Have ordered a relay so fingers crossed!

[Madgooner23]

Relay replaced - fan still on. Anymore ideas anyone?
 

[RogerT]

Learn to read a wiring diagram. Well worth it!



Available online from syncrosport.

Looking at this I’d also check the earth crowns beside the relays under the dash. Never hurts to give them a good clean. Clean all terminals then remove the crowns and clean under them.

I’ll have a good look at the wiring diagram just now.

[RogerT]

So the radiator fan is supplied by a permanent live (the 30 line at the top), which arrives at the fan via C7 on the back of the relay/fuse board, T1i single connector behind dash panel, the thermoswitch on the rad (which tells switches the fan on and off, and also supplies the second stage relay for the higher speed 500w supply, then through T2l (double connector behind dash) which takes it through a series resistor (N39 on the diagram), then to the fan. Then out of the fan to earth on the crowns on the A pillar under the dash. So if power is getting to the fan, and no one has mucked up the wiring, that points to the thermoswitch, which you have already replaced. I’d take the plug off the thermoswitch  and see if there is continuity between pins on the switch in the rad when it’s cold (3 pins if you have the correct turbo diesel wiring, I don’t know how they are arranged but the diagram marks the 3 for the feed, and 1 and 2 for the output - you don’t want continuity between 3 and either 1 or 2 until the rad is well hot). 

also check the integrity of the plug, after disconnecting the battery. Again there should not be any continuity between 3 and 1 or 2.

[davidoft1]

How long is the fan running after you switch off the ignition?

[RogerT]

Yes it does. Have ordered a relay so fingers crossed!

If it stays on when the plug is off the thermoswitch then there is a short, hopefully in the plug.

[Mocki]

How long is the fan running after you switch off the ignition?

The radiator fan is not wired through the ignition switch , it, like the brake lights are always live .

[davidoft1]

How long is the fan running after you switch off the ignition?

The radiator fan is not wired through the ignition switch , it, like the brake lights are always live .

Exactly the point f the question, if it’s running on for 5 mins when the engine is off it’s normal , if it’s 2hrs it’s not

[Mocki]

Argh right , i misunderstood you