Mechanics

HIGH PRESSURE SWITCH

Ford Escort

Ford Escort 97, SE, I need to by-pass the high pressure switch to check the switch and compressor. This switch is a three wire switch. Anyone know which wires I should jump?

Also, the dealer wants $60 for a new switch. Autozone, Checker, etc. Says they can't get one aftermarket. Any suggestions? Any Ford Techs know why other cars have a high pressure switch that costs $10 and this one is $60?
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DRPR1
May 23, 2007.



I tried this on a different car than yours but it should work. You ned a volt/ohmmeter. Unplug wire connector. With car and AC on check each wire for voltage to ground. It would probably be 5volts dc or 12 volts dc. Turn car off. Try jumpering that wire to one of the others and if that doesn't work try the other one. Check the other wires first to make sure it's not a ground. You wouldn't want to jumper to a ground wire. I don't think it has a ground going to it though.

Tiny
Rudpro
May 24, 2007.
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

Tiny
DRPR1
May 24, 2007.
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!

Tiny
DRPR1
May 24, 2007.
Sorry, I can't find a wiring diagrm that shows the AC circuit fully. The CCRM relay controls the compressor clutch, and the high pressure switch will also keep the clutch from being energized. I don't know if the high pressure switch is tied in to the same CCRM relay. Check the color of the wires at the switch and compare to the wiring on the relay. Check the wiring on the switch for voltage, I would think there would still be power to it even with the CCRM relay not working.

Tiny
Rudpro
May 24, 2007.
Also, the compressor won't come on if there is not enough refrigerant in the system. Fully charged, with the car off you should have about 70psi on the low and high side, they should be equal. I'm just bringing this up because you changed the compressor and it won't come on, and you can't fully charge the system without the compressor running.

Tiny
Rudpro
May 24, 2007.
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!

Tiny
DRPR1
May 25, 2007.
Jump in Justanold, this is stumping me too. According to your gauge readings, the system is overcharged. Except you said you only added 3/4 of a can to the system. That's what is stumping me. 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. 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. If the orifice tube is plugged, that could be giving you the high pressure readings. Also, where is your low pressure port located. Is it on the accumulator. If it is, there is a slightly different filling procedure. Let me know how it goes.

Tiny
Rudpro
May 25, 2007.
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.

Tiny
DRPR1
May 26, 2007.
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!

Tiny
DRPR1
May 29, 2007.
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?

Tiny
DRPR1
May 30, 2007.
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