Radiator fan always on (Page 1/1)
tmadia DEC 30, 12:49 PM
Only had my Formula for a couple months and I just charged the AC. When I turned on the AC the rad fan came on, as it should, but did not turn off when I turned the AC off (engine is cold). I removed the fan relay and it turned off, I have a new one on order in case it's stuck. If I have the relay in now, no matter the engine temp or the fact that the AC is off, the rad fan stays on as long as the key is on.

Is there a switch in the AC circuit that has to do with pressure that turns the fan on? Anything else I should check?

Thanks!
Blacktree DEC 30, 01:13 PM
There are 3 things that can activate the fan relay.

1) The radiator fan switch (on the intake manifold)
2) The HVAC control panel
3) The fan switch on the A/C compressor

All 3 of those things will have a green wire with a white stripe. Grounding that wire activates the relay. You can try unplugging each one, to see what is keeping the relay active. If all 3 are unplugged and the fan is still on, then the relay is probably stuck.

Also note that the HVAC panel switch and the compressor switch are redundant. Either one will activate the fan relay, when the A/C is turned on. So for example, if the compressor switch is stuck, you can unplug it as a temporary fix.

[This message has been edited by Blacktree (edited 12-30-2019).]

tmadia DEC 30, 01:34 PM
Awesome, thanks!

I'll do a little troubleshooting and see what's keeping it on.
Spadesluck DEC 30, 06:54 PM
I had this same problem with mine. It turned out to be one of my AC sensors.
creaky78 DEC 31, 11:48 AM
Same problem on my 87 GT. I unplugged the wire from the compressor, problem solved.
TXGOOD DEC 31, 01:22 PM
Mine does the same.
With the newer switches that go on the compressor you leave the ground disconnected or the fan
will run constantly.
tmadia JAN 05, 01:35 PM
Well it turned out to be the sensor in the compressor, or at least how it was wired up. It was one of the newer ones with the ground wire and as soon as I removed it the fan seems to work normally.

I'm not sure if that will make the high pressure switch stop working but for now it seems fine.

Thanks everybody!