The switch is the low pressure cycling switch. Switch closes, compressor clicks on, runs until pressure drops to certain level, then opens. This is what keeps the cooling even. The switch can be by-passed by putting a jumper in the switch connector. By doing this, the compressor will not cycle, and will run all the time. The switch can be changed without discharging the system. It simply unscrews.

With the cooling level changing with outside temps(ambient) I would suspect a low refrigerant charge. I just re-charged an Explorer. Same symptoms, kind of cold in cooler temps(morning), and almost no cooling in the heat of the day, and the compressor never shut off. Low side pressure was around 35lb, just low enough to still cool some, but never cold.

Get your friends gauges, get the pressure right, then go from there, is what I would do.

The clutch can be changed without the loss of coolant. Take the nut off the outside, remove the plate. The clutch itself is held on by a snap ring. You will need a snap ring tool as it is inside the clutch coupling. Depending on the location of your compressor, removing the snap ring may be hard to do. If it is down low, remove the compressor from its mount, and stand it on end. This will make it much easier.

Expansion valves, and variations of, are still in use today.

As an aside, the orifice tube should be red for Fords. The blue one works, but the red one will cool better. jd

 

On other models I have worked on, you could change the clutch without discharging the system. There are special tools to remove the clutch. I haven't looked at mine real hard yet since it still works (kind of). I was able to replace the clutch on the wifes Honda without discharging, I hope that the process will be as easy.

It still could be one of the other recomended repairs, but this is where I plan on starting my trouble shooting process. AC isn't all that important to me. Since my other trucks dont have it at all, I've gotten used to not using it.

Hope this helps and just doesn't make things more complicated.

 

I checked the A/C with the gauge on the can that you fill and it shows if your system is low full in the warning or in the alert. It showed with the a/c running full blast at idle right at the max full line when reving vehicle the gauge would drop to about 3/4 full. Tonight when driving home we paid attention for 15 miles it blew real cold. Then for about a mile it quit blowing cold and back to blowing cold after that mile. It blew for 3 miles cold then back to not cold at that point I was pulling in the driveway and the compressor was off. We turned the A/C on and off and the compressor would not kick back on and the dryer was not cold either but at that point the A/C had not been blowing cold for at least for a few minutes. Do I really need to get the gauges are the gauges on the cans that much off? If so would they not be dangerous for people that was not aware of what they were doing? I hope this info helps. Could it be the switch on the dryer or the clutch I do not know how to tell? If it is the clutch can you buy just the clutch at the auto parts store? Thanks for all your info, those first 15 miles tonight it blew really cold I just want it to keep blowing taht cold.

 

You can buy just the clutch, but they are expensive. $120 to $200 bucks.

I plan on getting one from the salvage yard.

 

The cycling switch is only a couple of bucks. If you want piece of mind you can replace it.

I wouldn't replace the clutch unless I knew for certain it was defective.

Does the compressor cycle after the truck has been sitting over night?

If it cycles, the switch and clutch are working.

You need the gauges to check the high side of the system also. Just checking the low side doesn't always tell you all of the story. Plus, you need to know the actual pressure. The gauges you get with the kit cover a range of pressures as they used on various makes of vehicles.

I'm not sure about 91, but it may also have a high side pressure switch. I don't think it is the problem here, but it could also be defective. If the high side pressure gets too high, the switch shuts off the compressor.

If you get the gauges, connect to both high and low side with the truck not running. You should have equal pressure in both sides, usually over 100 lbs. if the ambient temp is over about 90 degrees.

The low side with the truck running should be around 25/28 lbs. with good airflow thru the condenser and a 1500/2000 rpm idle. High side 210/250.

If you add refrigerant, it is best to drive the vehicle to let the system equalize, then check the pressure for a correct reading.

Most everything you get in this thread will be assumptions, and guesswork, but maybe it will help you narrow down the problem. jd

 

I don't follow what you mean does it cycle after sitting over night. What it does is the same thing over again it will turn on and blow cold in the mornings on the way to work sometimes it does not give me any problems usually on the way home from work at night. If I can get the gauges and the readings are what you told me what will that narrow it down to? My brother called me the other night said his 94 Ranger started doing the same thing and somebody checked it out said freon was full and the compressor was turning off and on so the clutch was going out. I guess with the readings off the gauges it will let you help me narrow my search down a little more. I will try to get a hold of them in the next couple of days and check the readings. Thank you for all your input.

 

I don't know if it works the same in a truck/car as it does in other A/C systems - but if the controls are reading the feedback from a thermocouple it can mess up if the thermocouple (hereinafter refered to as a Temperature sensor...) is in a bad place.

It might begin to ice around the temp sensor, and take a bit to thaw out. At that point the sensor decides: "OH! It's warming up again..." and the system comes on again.

It sounds like the clutch is the answer this time, but the above is an idea to file away for later on.

It's kinda blatantly ridiculously easy to tell if the clutch is working or not though - because either the center of the clutch hub is spinning or it isn't.

And I will go this much further - if it's spinning it ain't slipping!


I dunno, I'm not standing there looking at it. But to me it sounds like an A/C controller problem.

 

Oh and by the way:

What you are calling the "CYCLING SWITCH" is in fact the "LOW PRESSURE DISCONNECT SWITCH" and it is there so that if you lose your refrigerent (and thus: OIL CHARGE) the compressor cannot keep running and destroy itself.

It's a safety feature. It's got absolutely nothing to do with variable temperature settings.

If all else fails, go to the virginia chapter forum here at FTE and holler for LARRY MANTTA.... That man is the absolute ANSWER to any A/C question you will ever have, trust me.

 

Crap!! Here we go again.

CYCLING CLUTCH/ORIFICE TUBE SYSTEM - The exiting liquid is sent via a small liquid line DIRECTLY to an expansion ORIFICE TUBE. The orifice tube is fixed, therefore the proportional pressure drop across it will constant. This type of expansion device must work in conjunction with a clutch cycling switch. Because the pressure drop across the orifice tube is constant, the switch is used to maintain the system low pressure side in a certain operating range. The cycling clutch switch, through various pressure changes in the system, turns the compressor off and on during normal operation. A typical operation would have the switch turn the compressor on at about 45 psi and off at 25 degrees. This would maintain the evaporator refrigerant at temperatures around 35-45 degrees F.

http://members.tripod.com/acguy2/the...Orifice%20Tube

jd

 

You're not thinking about the temperature feedback sensor that reads cabin temperature. And right here is where I'm going to call in Mantta - because I think you are posting bad info.

With any luck Larry is on the way.

 

I never said anything about any sensor. The quote is from the posted link. This is standard a/c operation. I found this link in about 15 seconds, and posted it, because I can see where this is heading. Call whomever you want. Your suggestion on the thermocouple is "bad info" as these systems do not have one. This site is beginning to suck. jd

 

See my quote from the link in a prior post. Read the link if you want further info. Cycling means the compressor will turn on, run for a bit, then turn off keeping the pressure in range as stated in the quote. If the compressor is turning off and on, the clutch is ok, and the low pressure cycling switch is working. This is not to say that the switch isn't defective as it may be sensitive to pressure/temperature. I had one that was sticking, and worked intermittently. That is why I suggested changing it for peace of mind.

I'll let Greywolf take it from here. Good luck, and I hope it turns out to be something simple. jd

 

Yup, bad tech info posting/incorrect tech info posting have become a disturbingly regular occurance here in the Ranger forum (no, not this entire website, HERE) since early this year (2006). I joined FTE back in 02/03 and I can see what has happened. And it does suck, no doubt. It drags down a once great tech info forum as a whole. On a positive note, there has been some recent improvement; hopefully this trend will continue. As I said a few weeks back, "no answer is much better than a wrong answer". This statement has the most bearing on the man acting on the quality of the tech info given (or lack thereof).

*Wolf, if you would like to talk about this PM me with a phone # and I'll do whatever I can to help.

 

Lets keep things civil please.

 

I will go and pick up one of those switches and my friend is bringing me the gauges and I will replace the switch and check the readings and let you know what I found again thanks for your help.