To start I would like to say that I have a 2007 F150 with the 4.6L engine. Recently my ac stopped working. I don't hear the compressor turning on. I read a bunch of posts on trouble shooting this problem and would like to clarify a few things before I proceed. I have checked the fuses and a/c relay and they are both good. I have also taken my truck to a shop where they tested the pressure in my system and they said it was good. So now I want to start testing the two switches. The one by the fire wall on the accumulator (a/c clutch cycling pressure switch) is no problem as it only has two wires going to it. So all I have to do is put a paper clip and short the two wires in the connector to see if that will turn the compressor on. The other switch which I found is on the compressor-to-condenser discharge line, and it has 3 wires going to it. This is the A/C pressure transducer sensor. The three wires going to it are 1. signal return 2. reference voltage
3. AC high pressure cutout signal.
My question is how do I test this switch? What 2 wires do I short out in this switch to see if the clutch comes on. And just to clarify is this what people are referring to as the high pressure switch? or is there another switch that I missed? Thanks in advance, BART

 

Anybody?????? Someone has got to know this. There are all kinds of post where people test the sensors. I don't want to short out the wrong wires and cause more damage. Thanks

 

That sensor is an input to the computer. You probably don't want to mess with it unless you know what you're doing. It's not a switch, it's a pressure transducer that outputs an analog voltage that is in proportion to the pressure. The PCM then converts that analog voltage back to a digital value that can then be read with the scan tool (ACP_PRESS PCM PID).

Activation of the compressor is not a simple, straight forward process on the newer trucks. You REALLY need the factory workshop manual and schematics to work on it.

 

ok..., I guess i will jump the cycling pressure switch and see if that does the trick first and maybe get direct power to the a/c coil to see if it energizes. If both things function, then i dont really know where to go from here. I will test these two things out today or tomorrow and go from there. Thanks

 

You can also swap out the A/C clutch relay.

 

Did you ever come to a conclusion on what to do?

 

On my 2004 f150 with no power to the ac. My problem turned out to be a bad instrument cluster. My pick-up has automatic climate control and apparently a/c circuits are tied in to the instrument cluster. I replaced the instrument cluster and the a/c now has power and is working fine.

 

Since you FAILED to identify what you have, your comments are not useful and probably do not apply to the vehicle under discussion here.

Why did you feel compelled to post the same almost useless information in so many threads?

 

After days of trying to find there was no power to the a/c compressor, it turned out to be the instrument cluster. Apparently a pick-up with automatic temperature control, the a/c circuit is tied in with the instrument cluster. I installed a new instrument cluster and now the a/c is working fine.

 

 

I'm not sure how to jump but I was having the same issue with mine and turns out the refrigerant was extremely low. I just got a can of the refrigerant and put it in and after a minute or two of putting it in the clutch started engaging again and has been working sense and that was a few months ago.

 

I don't know how old was this post, but I just wanted to thank you for your input. I had a mechanic check out my truck and he was telling me I had to replace the compressor ( $820) . I decided to do what you did and that worked out great for me. After a couple of minutes I could hear the compressor clutch engaging.