Radiator Fan Always Running

[Toothmother]

Hi Guys,
All of the sudden my 1981 Diesel Caddy Radiator fan is always running. It starts running the second I turn the key, even before starting. I replaced the Auxiliary Fan Switch and still have the same problem. What else is controlling the fan? Could it be a bad replacement Switch? I am no expert so any help is much appreciated. Thank you!

[TylerDurden]

Does your dashboard control panel include settings for AC? Some will run the fan if the selector is set on any AC position.

[Toothmother]

Hi TylerDurden,
Yes it does have AC and I will check when I get home, but I never had that problem before.
TYVM

[Toothmother]

Ok the inside climate fan is now controlling the radiator fan. If I turn it off the radiator fan turns off and if I turn it on radiator fan goes on. This never happened before. How can that be? TY

[TylerDurden]

I can ony imagine it's related to the AC.

I sold my caddy too long ago to remember how the setup totally works, but I'd explore the ac switches and relays.

[Fatmobile]

Really? The heater fan turns on the radiator fan? ha. That's a new one.

[Toothmother]

Yes I think it will be funnier to me after I fix it! It is true any ideas what it could be? I am not familiar with the A/C, it was removed and I don't remember having A/C is my Rabbits when I was a much younger.

[82vdub]

On Ole 82 that has factory AC, the radiator fan will run when the heater selector switch is set to AC, or if it's set to defrost - AND - the fan switch it lifted to the one higher position than off. So yes, the heater fan can and does control the radiator fan (although not 100% directly). I would suspect that your heater controls are set to AC or defrost, and turning the heater fan on will energize the radiator fan.

[Fatmobile]

If you pull the radio;
There is a plug on top of the heater controls.
I believe it's the one that turns on the rad fan when the controls are turned to AC.
Maybe unplugging it will solve your problem.

[Toothmother]

Thank you. I will try that this weekend. I did notice that the climate controls are not connected correctly. So labeling on the heat, vent are all wrong. So the a/c controls most be working the fan. I did notice that the fan always kept running after I turned off the engine, but does not do that now. Is there another control for the fan cooling when the temp goes up besides the one attached to the radiator? TY

[Tac]

Just a guess but could iy be one of the temp sensors?
Tom

[Fatmobile]

I don't think there is any other thermoswitch than the one on the radiator.

AC switches usually shut the AC off when engine gets too hot.