Re: Cooling Fans won’t shut off while running
Posted: Mon Jun 29, 2026 3:28 pm
I'm still a little unclear how you know the fans are running when you are driving down the freeway at 65mph? Maybe my ears are getting old, but I can't tell in my car unless I'm stopped or in a garage, etc., and even they I need to confirm by looking.Glassmuseum wrote: Mon Jun 29, 2026 11:50 am I did all of the following and same symptoms. Fans kick off after first 2 cycles then they just stay running until I turn car off. 92c Thermofan switch and 71c thermostat:
- Unplugged climate control unit
- Tried spare relay.
The only conclusion I can come to is that the temp at the Thermofan switch in the radiator is actually above 92c and never stabilizing below that mark once the car is warmed up. What could this mean? Reduced cooling capacity? The water pump is new. I’ve added lots of water wetter. This is the second radiator with the same symptoms. Second relay with the same symptoms. Second thermostat with the same symptoms (only difference is the gauge does show the car is running at a lower temp with the 71C). Multiple Thermofan switches with the same symptoms. Should I just decide that this is normal? Should I try to find a OEM thermostat that actually opens at 80C?
- pressed and depressed with the snowflake button switch while the fans were running
It is in the 90’s here but my 2 previous 944’s did this so this is confusing me. The fans always eventually kicked off even in 100 degree weather.
:To isolate it with 100% certainty, you could just remove the plug, short the low speed and/or high speed fan terminal to ground to force the fans on (so you don't overheat). Then use spade connectors on the disconnected thermoswitch so you can monitor with a multimeter to confirm the fan signals are actually shorting to ground and staying that way even with the fans on running -- i.e., that the fans are unable to bring the temps down enough to shut off the fans.
If you pull the plug off the thermo-switch, do the fans stop running?
'Good used radiator' gives me a bit less confidence in its cooling ability, but if you car is running on the first white hash, it sounds like it is cooling just fine.