I tried searching for this, but when searching both AC and radiator fan, so much unrelated stuff comes up I just had to ask...

My '88 GT will run the radiator fan the entire time the key is turned on. Also, when the engine is running the AC clutch is always kicking on and off on the compressor. If I turn the HVAC controller to OFF it stops, but if I put it on ANY of the other settings the radiator fan and AC clutch both start doing their thing. I can only imagine it's related!

Is there a common issue of why your AC system would be triggered all the time the HVAC is activated?

As I understand it the ac clutch kicking on is an issue regarding the amount of charge or restriction in the system.
Either low charge or a restriction in the flow.
But I'm no expert.

So even if you have the blower set to floor, (not AC) it triggers the ac compressor and fan?

My 84 only kicks the fan and compressor on in the AC position. Maybe a problem with you HVAC controll?

I have an 88 4cyl. So I can't be much help comparing A/C systems since they use different compressors. Here's my dropbox link for the 88SM, (and some other info). Should help some if you don't have one.

https://www.dropbox.com/sh/...pE5Xxg6X8P3Zspa?dl=0

You need to replace your HVAC control head.

quote Originally posted by Oslo: If I turn the HVAC controller to OFF it stops, but if I put it on ANY of the other settings the radiator fan and AC clutch both start doing their thing. I can only imagine it's related!

Many people don't realize that the A/C also runs in Defrost mode... but no, it shouldn't be running in Heater or Vent mode.

Patrick brings up a very good point here. When controls set to defrost it does cycle the AC, and as far as I understand, it does not run the radiator fan in defrost mode. Is that correct?

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"Because in a split second, It's gone"
Ayrton Senna

quote Originally posted by Ponnari: When controls set to defrost it does cycle the AC, and as far as I understand, it does not run the radiator fan in defrost mode. Is that correct?

I removed the A/C from my Formula when I got it (so I can't go check)... but I believe anytime the A/C is running (including while in Defrost mode), the rad fan is running. I'm sure someone with their A/C still installed will easily be able to clarify this.

[This message has been edited by Patrick (edited 05-21-2016).]

The cooling fan runs whenever A/C or defrost is selected on the HVAC head on an 88.

The O/P has a defective HVAC head.

I checked the 88 FSM wiring diagrams, if his description of the problem is accurate, the only thing that could cause this is the head.

Thanks folks. I have an '86 parts car, so I'm hoping the control unit in the dash is the same as my '88. I'll try swapping them out.
If that doesn't do it I'll bring it to a shop that does AC work and get their input on if the system is too full or not full enough and go from there.

Uh-Oh, my AC is working and has been fine since it was fixed about 4 years ago. But my radiator fan does not run in defrost, it only runs when control is set to AC max, norm, and b/l. BTW, this is on my 86 GT. My others don't have working AC.

quote Originally posted by Ponnari: Uh-Oh, my AC is working and has been fine since it was fixed about 4 years ago. But my radiator fan does not run in defrost, it only runs when control is set to AC max, norm, and b/l. BTW, this is on my 86 GT. My others don't have working AC.

Not sure about the 88's. But on 1985-87 V6 models with AC, the radiator fan does NOT run with the defroster even though the AC is cycling. The radiator fan only operates on Max, Norm, or Bi-level.

Thanks donuteater306, that's what I always thought, thank god I don't have something additional to fix!

[This message has been edited by Ponnari (edited 05-22-2016).]

quote Originally posted by donuteater306: ...on 1985-87 V6 models with AC, the radiator fan does NOT run with the defroster even though the AC is cycling.

Interesting. Thanks, I learned something today.

A jumper wire can be added to the circuit board on an early HVAC head to enable the cooling fan to run in DEFROST mode.
Sorry, can't post pics from my phone....

quote Originally posted by olejoedad: ... defective HVAC head.

I assume the "HVAC head" is the control panel? I haven't heard it called that before but have heard car stereo decks described as a head unit.

[This message has been edited by 2.5 (edited 05-23-2016).]

OK, control panel.....

quote Originally posted by Oslo: Thanks folks. I have an '86 parts car, so I'm hoping the control unit in the dash is the same as my '88. I'll try swapping them out. If that doesn't do it I'll bring it to a shop that does AC work and get their input on if the system is too full or not full enough and go from there.

All years of heat/air controls function the same and will plug right in. 84 units have different color buttons, but they also work the same way.

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Rod Schneider, Ball Ground, Ga.
"You can't have too many toys!"
1988 Fiero GT
1988 Porsche 928S4
1987 Corvette
2001 Chrysler 300M
Van's RV-6 airplane