The 3 pins are one is ground one is for the fan and the other is for the compressor.

 

I donĀ“t understand the design. Why does the pressure switch have a signal for the fan? The objective is to measure the pressure on the high side. The fan stages are controlled by other pins directly from the ECU. Is the fan signal on the pressure switch some kind if feedback to the ECU telling it that the fan is effectively spinning, in case the relay goes bad?

 

I never really looked into the circuit that much but I know thats how it works.
I have had bad high pressure switches that only the compressor would come on but not the fan so the A/C would only work till the pressure got to high then shut off.

And I have had bad high pressure switches where the compressor would not ever come on but the fan would work.

 

Tech, thanks a lot. You have been very helpful as usual.

Regards

 

the radiator cooling fan sometimes doesnt work. i can turn off the car wait thity minutes- restart and it SOMETIMES runs. can someone please give input. this is college daughters car- third kid to take through college.

 

When you turn on the A/C compressor, does the radiator fan kick on automatically? To test the radiator fan which plug from to relay do you connect directly to a 12V source? Left, right or middle? What number goes to what battery terminal? (+ or -)

 

When you turn on the A/C compressor, does the radiator fan kick on automatically? To test the radiator fan which plug from to relay do you connect directly to a 12V source? Left, right or middle? What number goes to what battery terminal? (+ or -) I'm trying to discern whether I need a new fan assembly, relay, or switch. It's been an intermittent problem for me for a while...