1997 Explorer "white" AC system troubleshooting

[allmyEXes]

I am at the point on our 1997 Explorer, the white 4.0 one. The nice truck that has had timing chain repair, rack & pinion R&R etc.
Earlier armed with a jumper wire and a new 12oz can of 134a, I jumped the circuit at the pressure switch. I totally assumed that the AC compressor clutch
would engage and stay engaged. It energizes for less than a second and that is all it will do. So, there is no point in piercing this new can of refrigerant.
Is there a relay in the circuit that may need to be replaced and is that maybe why the system is not working? I checked to see if there is refrigerant pressure
at the port and there is. Is there anyone that has worked on these Explorer systems and would know more than what I'm seeing in front of me?
I have a few more minutes to search. I will be back late this afternoon and hopefully I'll have a little more insight.

 

[allmyEXes]

I found one large relay in the fuse and relay box under the hood. It is called a WOT AC relay. I swapped it with the blue '97 and still
does the same thing. AC clutch just pulls down for less than a second and then back to the off position. I'll have to get back to this later.

 

[FordFlintrock]

I assume you are jumping the 2 wire low pressure switch on the accumulator. If there is a blockage in the system the high pressure switch would be cutting it out. Only by hooking up gauges will you verify this possibility occurring.

 

[C420sailor]

Definitely need gauges.

The WOT relay cuts the compressor out at wide open throttle

 

[allmyEXes]

@FordFlintrock Except the system won't put out pressure if it won't turn on. I'm jumping the low-pressure switch at the accumulator.
I have gauges, but they are not portable. I hurt my back loading and unloading this beast with two other people. It has 4 tanks. 2 for recovering old refrigerant, r-12 and 134a and 2 places for 30# tanks of refrigerant. I'll never purchase a 30# cylinder of r-12. I guess that I'll remove the refrigerant and go through all the steps to refresh the system starting with an orifice tube. I may just wait until spring. Thanks for you guys' input. I was hoping for an easy fix. It never is. This is our shop's pre 2000 machine with very few hours on it. One vacuum pump inside as well as 4 refrigerator looking compressors and a bunch of lines and solenoids.

 

[FordFlintrock]

If there is a blockage one second or so of running is not out of the realm of possibility for hitting the high side limit, they pump up fast.

 

[allmyEXes]

It's barely even a second. I'm not an AC man by trade but if the orifice tube is a mess, I assume that the compressor could be shredding itself?

 

[FordFlintrock]

Getting way ahead of ourselves. Gauges first.
Check high side pressure. Check high side switch integrity/function. Then into clutch, wiring issues, etc.

 

[allmyEXes]

@FordFlintrock It is later than spring but I've finally been able to get nosed up to the AC recovery/recharge machine. I wish that I had read this before I've done what I have. Here is where I'm at.
I didn't have the gauges attached and watch them as I should have tried to engage the compressor. There was some refrigerant in the system. The low side gauge showed 60#s when I started the evac. It removed all of the refrigerant but didn't see any oil come out with it. There are no oily leaks at the connections. I removed the orifice tube and there was just a little metal but not enough to clog it. I replaced the orifice tube with a new one then pulled a vacuum and the system passed the leak test. The low-pressure switch wiring connector is Jumper'd but the compressor clutch still short cycles. I thought this to be odd because there is currently not any refrigerant in the system.

 

[allmyEXes]

I'm at this point in the diagnosis. Testing high pressure switch
I'll have a little time to work on it Saturday. The one lift at work is currently empty which doesn't happen often, and the AC machine is right in front of the available lift.
We have an extreme heat wave coming and I have been driving my wife back and forth to the big city for chemo treatments and fluids two days in a row after the chemo day. I can deal with the heat as long as the vehicle is moving. But I'm concerned about her having to deal with the high temps to come.
parked here for my later reading

 

[410Fortune]

You can jumper the high pressure switch just like you are the low side

With the high and low side switches jumpered and the engine running, dash switched to ac max, the compressor should turn

However after ii vacuum the system
And hookup the new can of refrigerant to the low port, the can itself should proved enough pressure for the compressor to run
It should run for a few seconds and suck in some Freon
Then the pressure will rise again from the pressure in the can, the compressor will kick on and short cycle again sucking in a bit more Freon
This continues until the compressor no longer short cycles and you have added 30oz of Freon

The low and high pressure switches are wiring in series
The wire travels through the low switch, over to the high switch and then to the ac relay

They are simply closed when there is adequate pressure (connecting the two wires together) adequate means not too low and not too high

For testing you just jumper them

In 97 the pcm disables the ac relay at wot
The wiring in 97 is complex more complex then later years, with 3 wires going to the pcm ac related

I will post the 97 ax wiring schematics so you can check the fuses and for power and signals at the ac relay

 

[410Fortune]

96/97 explorer ac wiring

 

[allmyEXes]

@410Fortune Thanks Jamie. My book that would be the closest to what I have is the "special" early 1997 release for the Mountaineer. I'll compare and note inside the front cover if it is the same. Also, the book is not with me at the moment so thanks for the diagrams. Before the sun went down, I looked under the hood and saw that it is a 2 -wire high pressure switch. Also, from Inet searching that it is normally closed. Thanks for the late-night post, late night for me that is. It was already lights out here when you posted at 7:30 to almost 8 ish your time.

 

[allmyEXes]

I have swapped relays and bypassed the high pressure switch and the AC clutch still short cycles if the AC/norm/def switch is already on then you turn the ignition switch to on. Now when the AC switch is in the off position,you turn the key on and switch to AC, max, normal or def, it will not short cycle.

 

[410Fortune]

So it works as it should sometimes? But only with high pressure switch bypassed?

Is the ac cold?

 

[allmyEXes]

@410Fortune There isn't any refrigerant in the system. The clutch will never engage more than a half a second. Nothing continuous in order to draw in the refrigerant.
The circuit from the ac/heater control runs to the AC low pressure switch which I have hot wired to the high pressure switch that is hot wired too.
The WOT relay (pin 30) is getting power from there and splits to pin 41 at the pcm. To me that would be power into the pcm. Wire 361 (red) power wire goes into pin 85 on the AC relay and comes out on pin 86 of the relay and goes into the pcm on pin 69. Relay pin 87A, wire 347 goes down to the compressor.
Something would have to be switching the normally closed relay open making it disengage.

 

[allmyEXes]

I have just read through this AC troubleshooting thread and decided that I have one of 2 issues. Either the wire #331 going to pin #69 has power getting to it somewhere or it is a pcm issue. I'm not a parts swapper by nature to find a problem but when one has extra parts at his/her disposal, that sometimes is the best tool. I'll be taking an extra 1997 4.0 SOHC pcm to work with me today along with the compressor clutch pigtail from my dead blue 1997 EX to swap pcms first to determine if that is the issue and/or fashion a test pigtail from the extra compressor clutch pigtail to ground one end and power to the comp clutch via pin #30 with the relay removed.
?Do I need the compressor clutch diode in the circuit and where is it located? Maybe wrapped up in the harness?
ADDED 30 minutes later. I could just remove the relay and make a jumper wire with flat male connectors (MDD22-250) to jump from Relay pin 30 to 87A.

 

[410Fortune]

The ac clutch diode is shown on diagrams but I also do not know where it is, likely because I put a 97 pcm into a 05 ranger hhahahahaha usually a diode would be installed in the pjb but in 97 there is only one and it is for the pcm

 

[allmyEXes]

I'm imagining a diode small enough that it could be wrapped in the harness.
I was unable to remove the blue '97 pcm and bring with me. Lack of tools at home. My "road" box that I was keeping in the blue '97 Ex got moved to the '97 Mountaineer which was here at the shop where I am now.
I think the simplest test is to, in the relay/fuse box, jumper the leads on pin 30 and 87A. Later I'll put the relay back in and swap pcms and see if that will fix it back to "stock".

 

[amj441]

The diode should be located in the harness itself.