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Nissan Frontier A/C Triple Switch

Q. Hi Vincent, First of all, I would like to thank you very much for providing a place for others who are in need of getting the honest and right answer for their cars' troubles. I have learned a lot from you. Thank you again. Now, I have a question that I need your help. My car is a: 2000 Nissan Frontier, 3.3 liter V-6, Automatic transmission, 39,000 miles, ABS brakes and A/C.

Nissan Frontier A/C Triple Switch

There are two fans that remove heat from engine; one is electrical and another one is run by the driven belt. I have a diagram that show the electrical fan is controlled by a switch that attaches to the top of its A/C accumulator.

To my understand that the switch will turn the fan on when it senses pressure built up in the accumulator - that means the A/C is turned on. With the diagram, I have traced the wire and was confirmed that the fan and its relay are working. When I shorted one of its ground terminal at the switch to ground, the fan would run.

Since the truck has extended warranty that I purchased for over $700.00, I brought the truck back to dealer to claim how come the fan does not work when the A/C is turned on. They charged me for $50.00 (deductible) and said there's nothing wrong with the fan. They said that the switch on top of the A/C accumulator would turn the fan on only when it senses the right temperature.

I was not convinced because there's no temperature switch that controls the fan at all. I have wanted to see what they said was correct. I have driven my truck with A/C on for 15 minutes at slow speed, 20 mph, and with a lot of stop and go. The fan never ran once. Of course, outside temperature in Houston nowadays is way too hot in summer. Also, the A/C is working and blowing cool air fine. The driven belt fan is working, too.

Please advice. And what is that switch located on the top of the A/C accumulator? Thank you again greatly for your help. Please advice me soon before it's too late to bring the truck back without charging for another $50.00.


A. That switch is the High/Low Pressure switch. It is there to cut out the A/c compressor if the A/C pressure get's too high or too low. It also controls the electric cooling fan. This is to prevent damage to the A/C compressor. Hence the name Triple Switch.

If the A/C line pressure gets too high, the electric cooling fan will come on. If the cooling fan does not lower the A/C line pressure and it continues to rise, the triple switch will turn off the A/C compressor. In theory, as long as the A/C system is working as it should, and since it is a relatively new system, the electric cooling fan should not come on.

If you ground the black wire at the triple switch, the electric cooling fan should come on.

Nissan Frontier

Additional Information provided courtesy of ALLDATA

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