Ford high pressure switch

Hi!

I replaced the compressor, etc.

The last item to be tested is the high pressure switch. I was told it was bad but wanted to test to verify.

The switch is a three wire switch. Do you know the functions of the three wires? Which should I jump to bypass?

Thanks

RUDPRO,

Thanks for the tip. Will the AC work with the High Pressure switch disconnected? I am working on two electrical issues at once. And that is tricky since they can effect each other. The AC won't work with the bad CCRM relay and I can't test the relay fix if a defective high pressure switch won't allow the compressor to come on.

Wil there be power to the switch with the AC off? Then I could still bypass the switch to make sure it isn't effecting the realy test.

Thanks!

O.K. Here is a mystery.

I flushed the system and blew it all out with compressed air, replaced the compressor, accumulator, orifice tube. Added 3.5 oz PAG 46 to accumulator and compressor per manufacturers instructions. Rotated the compressor 10 revolutions clockwise. Evacuated the system for 30 min. It held vacuum. I hooked up the first can of refrigerant, turne dthe AC on high. It sucked up 3/4 of one can and low pressure readings went to 250 while high pressure is at 150.

When the vehicle is off the balanced reading is 105.

The high pressure supply line is cold from the orifice to the passenger compartment but it is warm coming out. The accumulator is warm. No cold air is blowing from the vents.

The compressor cycles on for about 3 seconds and then off again. It is the low pressure switch on the accumulator that clicks to cycle it off and on.

I called one auto parts place and they are totally stumped.

I'll bet you are not. HELP!

Responses in text.
1) Except you said you only added 3/4 of a can to the system. This is correct.

2) You flushed the system and used compressed air to blow it out. I hope you used the compressor on the flushing cylinder and not blow the system with compressed air when you were done flushing. That would put a lot of moisture in the system. I did use the cylinder. The flushing unit I have is just a cylinder in which you can add cleaner and then it is charged with an air compressor. The cylinder has an air gun fitting on the end of the hose.
3) You should have removed the orifice tube before flushing. Normally, you remove it before flushing and clean the screen with a Q-tip. You should definately change it now. I did remove it before flushing and installed a new one after flushing. The old one had some debris but it wasn't plugged.

4) If the orifice tube is plugged, that could be giving you the high pressure readings..I will check that if you think that is the next step. Would the line after the orifice tube still be cold if the tube was plugged?

5) Also, where is your low pressure port located. Is it on the accumulator. If it is, there is a slightly different filling procedure. No, it is on the line between the compressor and accumulator. Could the accumulator be bad? It is brand new also.

Nice call!

I charged the system.

With the AC running I have 43 on the low side and 180 on the high side. The gauges fluctuate slightly (3 points or so back and forth)

The AC won't kick on unless I disconnect the High pressure switch. Then the radiator fan kickes into high speed mode (With the switch disconnected the high speed fan runs whether the AC is on or not). I tried to jump it but it appears to have no effect.

The other thing that is happening now is that in park at idle and in gear at high RPM everything works fine. At low RPM in gear the engine has a tendency to quit. Any thoughts?

Thanks for your help! You have been awesome!

Hi!

ANother problem.

Today the AC worked fine. For about half the day. I checked it with gauges tonight. It is completely uncharged. I obviously developed a leak. I took the system apart and vacuum tested various pieces. I had a leak at the accumulator connections. I took it apart and replaced the o rings. Then I had a leak at the compressor. I took it apart and replaced the o rings there too. I tested the system with vacuum but it lost vacuum after five minutes. Sigh.

Any ideas?

Hi!

Thanks for the response. Yes I used the green O-rings. I even bought a second set to replace the ones that came on the compressor and accumulator the second time around.

This morning I may have discovered the problem. It seems the O ring on the accumulator may have been bad. I replaced it and so far it is holding charge. I will let you know more later.

Any thoughts on the stalling at stop lights in geer?

Also, I tested out the high pressure switch. I have 5 volts at one terminal and 25 ohms resistance on another and nothing on the third. I tried to jump from 5 volts to the nothing but. Nothing seems to change.

Thanks.

Actually as long as the high pressure switch is disconnected the compressor will come on. When I attach it to the switch it stops the compressor. Of course what does happen with the switch disconnected is that the cooling fan runs at high speed whether the AC is on or not. And the engine is cold.

No luck on jumping the 5v to the 25ohms. It kills the engine immediately.

Thanks for the tip on the vacuum lines. I will check that.

No check engine light. The car has been vibrating for a while at stop lights. Prior to AC difficulties.