Mod that keeps the cooling fans on when the AC is on ***Split***

[David T]

Not running the fans would work but only if you are moving fast enough and even then it might not be enough. You must still have things set up so if the motor got hot enough it would turn the fans on. If you don't run the fans with the A/C you take a big chance of overheating the motor. Why would you not want to run the fans with the A/C?

[CFI]

Why would you not want to run the fans with the A/C?

Driving at highway speeds with a car that has an aux fan switch.

[FABombjoy]

I tried VSS-based fan shutdown and reverted to stock operation after a weekend, and that's with an aluminum radiator.

I found it doesn't seem to take much to disturb the airflow through radiator and temps will go up fairly quickly. Maybe at 70MPH+ it would be OK. I was driving behind a large truck at about 45 and temps went up to 217F before I turned off the AC to cool things back down.

[CFI]

I tried VSS-based fan shutdown and reverted to stock operation after a weekend, and that's with an aluminum radiator.

I found it doesn't seem to take much to disturb the airflow through radiator and temps will go up fairly quickly. Maybe at 70MPH+ it would be OK. I was driving behind a large truck at about 45 and temps went up to 217F before I turned off the AC to cool things back down.

Interesting. Thank you.

[Ron]

Driving at highway speeds with a car that has an aux fan switch.

Aux cooling fan or AC fan, switch?

When the clutch cycles off, the Otterstat will keep the cooling fans on if the engine temp is above normal temp anyway. So I don't understand what you are after either...

[hippieman9]

I can't find the documentation on the mod that keeps the cooling fans on when the AC is on, regardless of the compressor being on, or where the mode with set to. It is somewhere out there.....

Dave Mckeen sells a Fan relay that keeps the cooling fans on while the AC compressor cycles. I have it in my car and love it. takes the load off the electrical system.

[CFI]

Aux cooling fan or AC fan, switch?

When the clutch cycles off, the Otterstat will keep the cooling fans on if the engine temp is above normal temp anyway. So I don't understand what you are after either...

I have an aux radiator fan switch.

What I was wondering, basically, was “why do I need the radiator fans on when my AC is on?”

[Ron]

I have an aux radiator fan switch.

If the switch was already installed, my guess would be that a PO installed it as a backup since the electrical system leaves a lot to be desired. It worsens with age, and often blamed when neglect was the problem. Unless there is a problem with the OEM setup, the switch isn't going to help much, if any. ("Giving it a head start" only matters for a very short time....)

What I was wondering, basically, was “why do I need the radiator fans on when my AC is on?”

Because the fans blow through the radiator AND the condenser (a radiator for the AC system).
When Freon is compressed, it gets very hot. It is piped to the condenser which transfers the heat into the open air (just like the radiator does with heat in antifreeze).

[CFI]

Because the fans blow through the radiator AND the condenser (a radiator for the AC system).
When Freon is compressed, it gets very hot. It is piped to the condenser which transfers the heat into the open air (just like the radiator does with heat in antifreeze).

I understand. But the radiator doesn’t need help at speed. Apparently the condenser does. That’s all I need to know.

[Ron]

The condenser's input temps can get near 200F. And it will radiate heat to the already "hot" radiator, since they are almost touching, making them both need the fans. Not to mention the hot air (from highway speeds) flowing through one then the other...