Wiring electric cooling fan and A/C

[Moby]

When wiring an electric cooling fan should it be wired to turn on and run continously when the A/C is on or does it only need to run when the clutch is engaged on the A/C compressor? I've seen diagrams that have it both ways. Both are easy to wire, just wondering which is optimal.

 

[Tapage]

only to run when the AC clutch engages ..

 

[Tinker]

Just installed a solid-state controller that has a connection for the AC clutch trigger. When the AC clutch engages, the radiator fan comes on.

 

[Moby]

Just installed a solid-state controller that has a connection for the AC clutch trigger. When the AC clutch engages, the radiator fan comes on.

Interesting - what controller did you use? I've got a controller from Centech that connects to a temp sender and allows you to adjust when the fan comes on. The relay is only 30amps so I have it rigged to trigger a Bosch 75 amp relay. I've worked in a free wheeling diode to protect the Bosch relay (this is for a Mark VIII fan that draws 100+ amps on start up and 30-35 continuously). It also has an A/C input but it's not solid state... Just curious what you're using.

 

[Tapage]

Actually I prefeer use a manual switch to control the electric fan .. coz, cold mornings sometimes I use my Aircon .. but my engine is very cold .. so use the aircon without electric fan ..

When is necesary ( engine warmup ) switch on the electric fan ..

 

[Moby]

I actually just came across a variable speed controller that is just what I'm looking for. It varies the voltage supplied to the fan to try and maintain a fixed temperature. I never liked the idea of cycling the fan from 0 to 100% on, off, on, off and watching the temp cycle from 180 to 190, back to 180... This controller runs the fan at whatever power level is necessary to maintain the temp you pick. This keeps the amperage draw and noice levels down as well. It has a provision to run the fan at 50% when the A/C clutch is engaged. They also have a very detailed section on their site about the reliability and life expectancy of their controllers.

http://www.dccontrol.com/

 

[Waggoner5]

That controller is a quality piece. I have used them before. The AC wire works well off the high pressure switch to keep head pressures down and temps at idle down. You have to use a relay to convert the signal from a negative to a positive which is what the the controller is looking for.
Gary

 

[Tinker]

Mine's a 45A Flex-A-Lite with +/- AC input, radiator probe (no crappy bulb in the upper hose), manual override On &/or Off, programmable temp start at 60%, 15 sec delay at ignition on, 30(?) sec continue at ignition off:
http://store.summitracing.com/partd...&part=FLX-33054&N=4294860844+115&autoview=sku

 

[Tinker]

Tapage -
What's cold in Panama? It was 53F here this morning.

 

[Moby]

The AC wire works well off the high pressure switch to keep head pressures down
Gary

Good to hear some first hand feedback on the control, thanks! I'm not sure I follow the line above though. What is the "head" that you're refering to? The cylinder head?

I was thinking of just wiring the controller's A/C wire to the A/.C clutch "energize" wire that engages the compressor's clutch. I haven't looked at the wiring diagram for it yet but since it grounds to the body of the A/C compressor I assumed the lead was positive so I figured I'd just tap that wire. Is there a better way?

 

[Waggoner5]

The compressor head for the AC. You want to keep the high pressure down under 175-200. In high heat situations, the pressure on the high side will rise and trip the high pressure switch disengauging the AC clutch. This is because the condensor cannot keep up with the heat transfer. By attaching the fan control to this wire it will make the fan come on when the pressures get high thus allowing max air over the condensor. By attaching the controller to the ac clutch, it acts the same by keeping a constant flow of air across the condensor, thus keeping the high side pressures down and the compressor on. Either way will allow much better AC cooling at low speeds.
G

 

[Moby]

Great info, thanks!

 

[Tapage]

Tapage -
What's cold in Panama? It was 53F here this morning.

22ºC ........