Hi folks,
I'm going nuts with the AC in my 1995 Eddie Bauer Explorer with the Electronic Automatic Temperature Control. This spring I had a shop replace the low pressure switch, the compressor and clutch, the Accumulator/Drier, and the Evaporator Core Orifice. They flushed the system. They pulled a vacuum and let it sit for about 30 minutes to make sure there were no leaks add new oil and freon and everything worked beatifully until about a month ago. The air just quit working. I jumpered the low pressure switch nothing happened. I pulled the compressor clutch connection and there was no voltage. I even disassembled the clutch connector and tightened the clips to insure a good contact. Still no air. I ran a jumper from the battery positive to the clutch positive and the AC started up fine and cooled things down to frigid. It had cooled off down here in Texas so the temp was only about 68 degrees. I put the gauges on and non running they showed 68 psig pressure before I started which is about right for 134a. I jumpered the clutch and got 28 to 30 on the low side and 150 on the high side. I checked any fuse that was related to the heater or AC and they were fine. I open the power distribution module under the hood and found the the WOT relay that shuts the ac down when passing was hot. I could feel it cycling on and off every 1 1/2 or 2 seconds whether the sytem was jumpered or not. I replaced it but the new relay did the same thing. When I first looked at it in early September (95 degree ambient temperature) it did start running a couple of times on its own but only ran for a minute or so each time. When I worked on it this week a few minutes after I started working on it in 70 degree ambiant temps it ran okay for about 20 minutes after I jumped it and got it running. I pulled the jumper and it kept running okay. It quit and won't start on it own again the last couple of days. The EATC unit has a self test setup. You press the "off" and "floor" at the same time and then within 2 seconds you hit "automatic". A little revolving box tells you it is working and then it is supposed to show the error code on the display when it gets finished. I ran it several times and when it finishes it comes up with the same 888 display with all the functions e.g. floor, defrost, panel, defrost lighted and all the other stuff that comes up when you first turn the car on. There is no error code shown on the display. The Ford truck CD seems to indicate the error codes show up on the normal EATC display but I notice that there is what appears to be a code reader plug under the dash to the left of the steering wheel. Is there a code reader that has to be plugged in to that to read the codes? One last thing I noticed. If I pull the wot relay out of the power module while the car is running the idle increases about 25 0r 30 rpms and drops again if you plug it back in. Can any one think of something that can be causing these symtoms. OBTW the heater and all the floor, vent, panel, blower switches work fine.
Thanks for reading this novel but I wanted to give as much info as I could
Dick Downing

 

Thorough description, thanks.
The power flow for the AC clutch is: Fuse-message center-EATC controller-cycling switch-high pressure switch-WOT relay-compressor clutch-ground.
The WOT relay is a Normally Closed relay and is energised by the PCM to turn off the AC clutch when needed That's sort of backward from usual relay applications. The PCM opens the WOT relay by supplying ground to the Pink and Yellow wire at the relay when necessary.
It sounds like the PCM is cutting out the compressor all the time since the relay is warm. To verify this, Check for power to Pin 30 on the WOT relay with the AC turned on.

--If you have power at pin 30 and the clutch won't engage, put a jumper across pins 30 and 87a of the relay. The pins are marked on the bottom of the relay, put the jumper across the corresponding terminals in the socket. (I can't reliably read the wire colors without printing out the page from the CD, my printer is down right now). The wires appear to be DG\O and BK\Y.

If the compressor then engages, there is something wrong in the engine controls causing the PCM to cut out the AC clutch. This is often caused by a bad Throttle Position Sensor, but proper diagnosis is needed to be certain. Does your Chgeck Engine light ever come on? Are there any driveability issues?

--If there is no power to pin 30 on the WOT relay, back up through the High pressure switch and cycling switch checking for power. If there is no power getting to the cycling switch from the EATC controller(wire appears to be Pink), the EATC controller is suspect.

Hope this helps.

PS. You obviously have an electrical issue. The refrigerant system appears to be ok. DO NOT try to add refrigerant "just to see if it will help". It sounds like you're aware of this, but I needed to mention it to be sure. Too many folks grab the can of refrigerant at the first sign of an AC problem.