I am wanting to remove my mechanical fan and replace it with a second electric fan. I know the first one is controlled by a temp switch and turns on or off depending on the temp of the engine. The second one I want to operate only when the AC it turned on to keep air flow over the condenser. Has anyone ever figured out where to tap into a power that is only on when the AC is on to operate a relay to run the second fan.

The one and only wire to the AC compressor is the AC clutch control - I would use that.

 

This has been discussed a lot lately - a search would be a good idea.

 

GD

The one and only wire to the AC compressor is the AC clutch control - I would use that.

 

This has been discussed a lot lately - a search would be a good idea.

 

GD

 

So there is no outside pressure switch to control the pump?

 

So does the pump have its own built in pressure switch?

There is a pressure switch, but it wouldn't tell you if the AC was turned on or not. It's only there to cut the AC off if the system loses refrigerant charge. So if you wired to that, then the fan would just be on at all times.

 

I'm sure there is some relay's you could use also, but I'm not sure where they are located. Basically if the clutch is powered, then the AC is on. I would use the clutch power wire to power a fused relay circuit for your second fan. It's easy to get to, and it's in the same area as your fan will be.

 

GD

There is no switch in the compressor. My 86 FSM shows a pressure switch, states that it is main fan control. Also shows a low & high pressure switch. Those for the Hitachi A/C.

 

The Matsu************a A/C has a trinary switch. (I think it combines the functions)

 

Hitachi compressor is cylindrical, Matsu************a is more box / cube like.

There is no switch in the compressor.

 

It's not the compressor I'm refering to - it's the compressor belt clutch. It does have a switch - that's how the compressor is turned on and off when you select AC or Defrost.

 

Now that I think on it, there probably is a switch for the regular fan. I think the regular radiator fan is supposed to cut on when the AC is turned on as well. No idea where that's located tho.

 

GD

If I hook it strait to the pump the fan would be on only when the pump is on. When the pressure switch hits its desired pressure it would shut off the pump which in turn would turn off the fan, which is not what I would like. I want the fan on all the time if the AC or defrost button is pressed. Well I will do some more searching. Maybe in the mean time I will just hook the relay up to a switch in the cab that way if I have the AC or defrost on I would just turn it on.