Radiator fan staying on..help !!! Please

cliff · 03-18-2002, 11:12 AM

As the title says, the radiator cooling fan stayed on for a hour after turning the car off. I disconnected the battery till the problem is rectified. What could it be. Just started happening this morning. Relay ? If so, how do I reset a relay to get me back on the road. Also which relay is it. I am at work and do not have access to my manual which is at home. Car is a 88 951 stock.
Thanks for the help.

944S Boyeee · 03-18-2002, 11:50 AM

The relay is the BIG silver one closest to the windsheild. It will be listed on the bottom cover of the fuse box.

Pull this relay and if the fans shut off, then it's the ThermoValve Switch. If they stay on, it's the relay. The relay is pricey compared to the switch. The switch cost me $25 Canadian and it's located about 3/4 of the way down on the rad. You can either take it to a local gas station and they will change it (very quick, easy job) or do it yourself.

Don't forget to drain the rad!!!! Or make sure the guys doing it know that (may sound dumb, but many have been "soaked" while changing this). You don't have to drain all the way down, just enough that the switch is no longer covered in liquid.

Roger Hall · 03-18-2002, 06:21 PM

mine is an 81 924 so there will be some differences but the fans are switched on by the thermo switch check the switch or switches some cars have more than one the power is supplied three ways from the cooling fan relay, the ballast resistor, and the a/c switch if the thermo switch is good then it may be a bad ballast resistor is the fan runing at full speed or low speed

divezic · divezic's Garage

I had this problem recently. It was the thermotime switch on the left (driver) side of the radiator. When it fails it fails closed so the fan continuously runs. I got sick of removing the fuse every time I shutdown so I replaced the switch.

This is the important part...DO NOT OVERTIGHTEN THE SWITCH WHEN REPLACING IT. Guess which dummy stripped the plastic threads on the radiator. A new radiator ($275) and a torque wrench later I was back on the road.

Britwrench · 03-18-2002, 07:59 PM

I'd agree that it's likely to be the fan switch on the radiator.
However, on a Turbo it's not a "qucik, easy" job and I would NEVER let the local gas station touch it!!

The fan switch is obscured by the fan shroud, sometimes it will come out without loosening the shroud, sometimes it won't.

With the engine cold, remove the pressure cap and then replace it, this releases any residual pressure. You can then remove the switch and only minimal coolant will escape, make sure you have the new switch ready to go as you unscrew the old one.......
DON'T overtighten the switch, it only has to be barely more than hand tight. Run the engine when everything is back together to make sure the fans cycle.