Fan coming on after car is turned off.

Oahu911 · 11-11-2010, 02:35 PM

Today a fan on my 79 SC attached to the vents on my engine lid is turning on after the car is turned off. Its never done that before and its not real hot out...is this normal? I'm no mechanic and I don't even know if that fan is aftermarket or what. Its attached to what appears to be an aftermarket ac. It turns on for a couple of minutes, turns off for awhile , then back on. Any advice would be appreciated!

Thanks, David

Bob Kontak · Bob Kontak's Garage

A fan turning on after the car is off on a 79 is not factory. It is probably a condenser fan that is wired to a temperature sensor that is not "switched". Meaning that it is getting juice all the time from the battery and will run if the temp sensor says it is hot enough.

Is the fan in the engine lid?

I am not an ac or electrical expert but there are reasons the system may be running hotter now vs. the warmer summer months - e.g., low refrigerant. Search in the advanced search section and type in various terms relating to air conditioning problems and spend some time reading.

If you are happy the ac is running properly you can have the fan power feed moved to a switched connection - this has to be done by someone who understands the electrical load placed on that circuit.

I bet you just need some refrigerant.

Oahu911 · 11-11-2010, 03:29 PM

Thanks for the reply. I should have mentioned the AC is not hooked up. I went to pull the fuse but there is none in the AC fan slot. I think I'm just going to snip the wire for now.

Bob Kontak · Bob Kontak's Garage

Trace the wires if you can and see if there is an in-line fuse that you can disconnect.

Oahu911 · 11-11-2010, 03:39 PM

Oahu911 · 11-11-2010, 03:41 PM

This was on the car when I bought it...now I see how jerry rigged it looks!

911pcars · 11-11-2010, 08:07 PM

I agree with Kontak.

The PO might have transferred a condenser fan from an Asian import. Most use a temperature sensitive relay that, in addition to it working when the AC is ON, automatically switches ON when the engine compartment temperature elevates after shutdown, then shuts OFF when the temp. drops. If the fan doesn't switch OFF, the control circuit isn't working correctly.

Having a fan energize after shutdown is a good idea to reduce engine compartment temperatures. An improved control circuit would reverse the direction of the fan after shutdown and encourage rising hot air out of the area.

Sherwood