A/C problem

The problem is insufficient freon in the system. Fixing it is a two step process. (1) Find the leak. (2) Evacuate the system and fill it with the exact amount of refrigerant required.

If you were a redneck shade-tree mechanic, you might get one of those twelve-ounce cans of freon, that comes with its own recharge hose, and fill the system until you thought it was working properly. This might work, but for long-term satisfaction you have to find and fix that leak.

Earle

You don't really "know" that a system is leaking until you find the leak. Your typical shade-tree mechanic may not have the reasoning ability to connect chronic low pressure with a leak.

All seriousness aside, I fully agree but people are going to do, what they are going to do, and why do they sell those twelve-ounce cans of freon, that come with their own recharge hose, anyway?

It took me two cans of sealer/leak detector to find the leak in my Suburban, after two "certified" mechanics said they had it fixed, and seriously overcharged me for six pounds of freon. The experience led me to buy a vacuum pump and gauges, and almost to come out of retirement. The sealer, leak detector, and oil were all leaking down the drain from the rear air, onto the ground. ;o)

Earle

MPClark did pass the time by typing:

Without actually looking myself it sounds like your slightly low on refrigerant. That's normal for a system as old as yours. My 93 ZJ required a kick in the arse (3oz) back in 2000 or so and actually might need a checkup, hasn't gotten that hot yet.

There are two sensors in the AC system. A low pressure and a high pressure. the low one is located on the accumulator bottle, the high one on the ac pump output.

Be careful about how you measure pressure, a correct reading depends on outside temperature also. My guess is your at the very low edge of the scale. Also remember to correctly get the pressure you need to have the compressor running. That's done by jumpering the harness to the low level switch and settign the AC on max/recirc. Both the hoses going into the cab should be cold to the touch. If one is cold and the other warm then your low (or very overfilled). Always trust the pressure gauge.

If your not familiar with servicing AC systems it might be best to let a local shop do the work. Around here it's about 90$ for an AC system service.

For those that quote laws.. here is the EPA read

legality depends on the state (or country) you live in.

Alright, I went back to check all of that. After letting the engine an

A/C run for several minutes, I checked the pressure to be just abou

1. Then I felt the lines: the two going into the cab are slightl warm, the one going into the compressor is also slightly warm, and th line coming out of the compressor is too hot to touch. It's confusin me because whether there is a leak or not, the pressure is where i should be, so low pressure shouldn't be a problem I would think

-- MPClark

MPClark did pass the time by typing:

The compressor output line will always be hot. The return line from the condenser (little radiator in front of your radiator) will be cooler. That line runs back to the accumulator/expansion valve and after that should be cold, that runs into the cab where it goes through another coil called the evaporator, then back into the engine bay and to the compressor.

If you grasp the line going from the accumulator into the cab it should be darn cold/freezing. The line coming out of the cab to the compressor should also be cold (nearly as cold as the line going in, but not quite)

When checking pressure or filling you need to have the compressor running all the time, you do that by jumpering the lowside cutout harness with a bit of wire.

40psi is "normal" for about 75deg outside temp.

General charge chart. F Lowside psi

65 25-35 70 35-40 75 35-45 80 40-50 85 45-55 90 50-55 100 50-55 105 50-55 (this is where r134a peters out)

The shops measure from the high side.. BE CAREFUL, high side is HIGH.

F Highside psi

60 120-220 70 140-240 80 170-260 90 200-300 100 230-340 110 270-390

Your description tells me it's low on gas. But don't add a whole can. only add a bit at a time till the system starts cooling down.

One of these helps for the low side work

If the big line going to the cab is not cold, then you don't have enough refrigerant in your system. I do not have a good source of theory handy, but my basic air conditioning service manual says over and over again, that R-134a systems cannot be charged by the pressure method. "The only way" is to evacuate the system and then charge to the proper weight of refrigerant. I didn't get anywhere with my old Suburban until I started believing the authors of this book. Now, the AC has been working for two years without fail. (The new O-rings, compressor, hoses and orifice didn't hurt.)

You can charge refrigerant until the return line (the big one) from the cab is cold, and your system will work for a while, but it won't be right. You will either have too much or too little refrigerant in there, and combined with your leak this is going to mean a system that only works for a couple of months, if that. When your system is evacuated (which will happen soon, one way or the other) I recommend replacing all the O-rings and any hose that is wet with refrigeration oil.

Earle

ok you guys here goes,,, the line going from the accumulator to the evaporator should not be cold. It will probably be warm because it is liquid refrigerant under high pressure. The line coming back to the compressor should be colder than the other line. Two lines going into the cab. One warmer than the other, and....the one returning to the compressor should be the colder of the two. I'll have to check your 134 theory, but it's probably a mixed refrigerant, and if thats the case, it needs to be dumped and recharged as a whole because it is more than 1 refrigerant combined together, and they will leak at different rates. Thats why it must be dumped and recharged as a whole. I just can't remember the make up of 134a and whether this is a mixed gas or not without looking at the jug....

Earle Hort>If the big line going to the cab is not cold, then you don't have enough

also, if the corresponding temperature on the pressure temp gauge is more than 20 degrees F lower than the large line returning to the compressor, I'd say your low on gas. The lower the superheat # the more efficient the system is. As the temperature difference gets greater, that means less efficiency, thus low on charge situation.........use the gauge and the temps, you won't go wrong......... let me know how it all turns out..

Robb S wrote: