I have a `91 Explorer w/ the 4.0L (pushrod) engine and auto trans that has 150K miles. The A/C stops cooling periodically. i do not know if the compressor is actuallay cycling off during these times but I beleive that it is. It usually happens when the truck is fully warmed up and when driving at speed. Turning the system off and then back on seems to get it going again.

I understand that the compressor cycles off based on the low side pressure and is contolled by the switch at the accumulator. But, I also know that the compressor will cycle off if the idle drops too low and I beleive there may be a switch for wide open throotle (WOT). I don't know where those two switches are located and whether there are other components that might contribute to the problem. My thinking is one of these semors or switches is malfunctioning.

Mark

 

 

I believe that the computers interpretation of TPS voltage and idle speed is how it decides if you are in WOT or idle. No switches. Sometimes the pressure cycling switch is at fault and also the clutch coil can be weak. Replaced 4 today for this very reason.

 

Thanks for your comments.

If the engine management is simply using the TPS then that will mean that the compressor circuit is run through the engine management system. Right?

I tend to beleive the low pressure switch is bad because it will allow the evaporator temp to drop below 32 degrees. Does the system have to be discharged in order to replace the low pressure switch? Is there a way to check the clutch coil to see if it is weak?

Mark

 

No need to discharge system for switch. It screws onto a schraeder port. To check clutch coil you will need to catch the problem in action and not running and see if their is power to the feed wire at the compressor. Also if it has disengaged you can push in on the clutch plate and it should catch an start turning. This method is dangerous be careful.

 

I have quite the story on my air conditioner in my 92 Explorer…
I had the exact same problem with the A/C shutting off once the engine warmed up. What would correct it though was if I stood on the accelerator to get her to downshift, the A/C would cycle until the pressure built up in the system. So, I tested and tested again, the whole electrical system for the A/C. All of the wiring was fine, the WOT relay was fine, and the pressure switch was fine. I finally tested the coil, I ran power to one terminal and grounded the other, the same thing happened, I had to accelerate the engine to get it to cycle again. I ended up tapping the coil with a hammer or wrench, and it would cycle until I removed the power from the coil. Then I had to tap the coil again. I came to the conclusion that there was either a bad thermostat in the coil or a break in the copper winding. So I asked Ford for some information on the coil construction through their customer support E-mail address, they told me that I had to take my truck to the dealer. Exactly why I fix my truck myself, so I don’t have to spend $70.00 an hour at the dealer. So, I asked the guys at the Ford dealer if they knew if there was a thermostatic switch in the coil. They didn’t have a clue. So I broke down and bought a new coil. I installed it and took the truck out for a ride to test it, and here we go again, the same thing. So I tested everything again, from the battery through every fuse and relay. Everything was good. I was completely puzzled. Just out of curiosity’s sake, I took apart the old A/C coil to see what it had inside since you can’t return electrical parts. I had to completely destroy the thing to get it apart, just to find out that there was only a copper coil inside that could never disintegrate and NO thermostatic switch. What it was, were the aluminum connectors that the truck’s wiring harness plugs into. The copper wire winding goes through two small holes by the plug and two aluminum prongs with a small cut in the one end that pinches the copper winding wire that comes through the back of the coil housing. Looking at this just shows that it is a bad design. Just a small connection at these terminals caused corrosion at the copper wire and aluminum terminal which made for a bad connection. This would now make sense, when the engine was revved up or the coil was tapped with a hammer the vibration completed the connection and the coil would work. So I FIXED the BRAND NEW COIL by soldering the aluminum prongs right to the copper coil winding and haven’t had another problem with it since. It is just too bad that I had to ask and ask for this information that I couldn’t get and then spend $60.00 for a new but obviosly not needed coil. When I look on the bright side though, I have a $60.00 roll of copper wire now that I can’t use for anything except hang the brake caliper up when doing a brake job. I am sure that this happens to a lot of people though, their mechanic says that you need a new coil because it is weak so they replace it with a new one. Only to find that it will happen again in a few years. So before you spend money on a new coil, if that is what you are going to do, try this repair first. I hate to see anyone spend money on new parts that aren’t needed especially since everything seems so overpriced.

Hoppy

 

Thanks Hoppy for your comments.

Can you take the clutch and coil off with ease? How do you hold the compressor so that the clutch cneter screw can be removed? Once the screw is removed does the clutch simply slide off?

 

Clutch plate comes off after removing 5/16 head bolt in center. A puller is the best way to remove clutch plate but it isn't on tight so two screwdrivers can be used to jiggle it off. There are shims behind the plate and on the end of the shaft so be careful not to loose them. Next remove snap ring and pulley. Then snap ring and clutch. Shims are for setting 20 to 40 thousands air gap.

 

No Problem with the adviced

You can take the clutch and coil off by removing the 8mm. bolt on the centre of the clutch. To hold it, with the compressor and belt still in place, I pressed the clutch driven disc onto the pulley with my hand and loosened the bolt that way. If you have a big enough set of pliers, you can grip the outside of the driven disc with them. Once the 8mm. bolt is removed the driven disc just pulls off. Once you remove the disc, unplug the electrical connector and with a couple of screwdrivers just pry it off of the end of the compressor, I think I lightly tapped it off with a hammer. I am not quite sure if you have the same problem as I did where you had to solder the coil winding to the aluminum connector but if you are going to try this fix, you don’t need to remove anything. There is just enough clearance between the coil housing and the compressor to get inside to solder the connections. All you have to do is unplug the electrical connector then with a screwdriver, bend the small steel tangs on the back of the coil housing back carefully, as not to break them off. Pull the grey electrical connector coupling off of the coil housing straight up and there you have it, the two connectors are looking you right in the face!! Look down at the bottom of these connectors and you should see the coil winding coming through the end of the aluminum connector. Get lots of soldering flux down there and get your soldering iron as hot as it will get and give the solder to these connections. Make sure you get down far enough to bond the coil to the connector. Once this is finished, all you need to do is put the plastic coupler back on and plug it back in. If you removed the coil make sure you centre it on the compressor and lightly tap it with a hammer on the outside metal hub surface only until seated perfectly, you may opt to use a block of wood with a hole drilled in it for the compressor shaft and tap it on this way.

Let me know how you made out with this repair.

Hoppy

 

Don't forget the snap ring and the pulley. I forgot to mention that, you will need a snap ring plier set to remove it, or have some good skill at using needle nose pliers.

 

Let me know how you made out with this repair.

 

I have been so tied up with other stuff that I have not had a chance to do any of the things that need to be done on this truck.

My latest porblem started this past weekend and I have only had a couple of minutes to try and figure it out. As soon as the engine warms up it runs real rough, won't hold an idle, and stalls constantly. When cold it seems to run about as it is supposed to. I have disconnected the O2 sensor to see if it would run better but that did not help so I guess it is okay. Next step is to check the fuel pressure. If you have any thoughts on this I am all ears. I am hoping I can carve out some time this weekend to tackle this running problem then I will go on to the A/C issue.

Thanks,

Mark