Any GM mechanics onboard?

[mopar head]

I have a 2000 GMC 3500, work rig. The AC just recently stopped working.
I notice the clutch engauges then kicks out, it keeps cycling every 3 sec. or so. It`s trying to cool so I don`t think it lost refrigerant. No fuses are blown and relay seems to be working. I`d like to beable to fix this myself if possible, and preferr not to take it to any stealership.
Any help would be appreciated:?

 

[RedFish]

When they loose a small amount of gas, the low pressure switch will cause system to cycle off and on just as you described.

 

[toolmanmike]

Needs freon. It is a 134a system so you can get freon at your local parts store or even Wal Mart. Also, you obviously have a leak which may be obvious or very difficult and expensive to find and repair. I would add freon as per the instructions on with the kit. (some kits even have a pressure gauge) Monitor how long the system works and that will tell you how bad the leak is. You might be able to top off the system and it will last throughout the summer. Good luck. tmm

 

[mopar head]

Thanks fellas, that`s what the parts store guy was saying also. Just wanted to get a second opinion.

 

[Woods74]

Might be good to trace where that leak is coming from, a lot of the hobby/variety stores i.e Big Lots, carry 134a for a fraction of the price of auto stores and some have that UV detecter in them.

 

[mopar head]

Got a can + gauge, When the compressor cycled off the gauge showed in normal range, 40-45, when cycled on it would drop to about 15lb-. I gave it a little shot and went a little higher when compressor cycled off, getting into the too much range, so I was afraid to add any refrigerant. It would seem like no loss of refrig? I just don`t want to over charge it. I`ve never messed with ac stuff before. Is this normal when comp. cycles off, pressure goes up? Go ahead and keep filling? anybody? sign,clueless:sad5:

 

[RedFish]

When the compressor stops, the pressure slowly equalizes throughout the system. When the compressor runs the high side goes up, the low side goes down. If the low side falls too far the low pressure switch stops operation. 15 is too low. The low side gas need to stay above freezing ( pressure and temp are close to equal ) when the compressor is running. If the high side goes too high, like overcharge, and the low side still goes too low, the fixed orifice tube is clogged.

 

[mopar head]

Thanks Benny, I assume to access the tube would mean to discharge the whole system? and where would the tube be located?

 

[toolmanmike]

And if the orifice tube is plugged the compressor is going south. (That's where the material probably came from that is plugging the orifice) Like many AC problems, they can so south and get real expensive real quick. If the compressor launched it's guts, you are looking at a new compressor, complete system flush, new reciever-drier, orifice tube, and Freon plus labor.

 

[mopar head]

Ouch, just what I DID`NT want to hear! Thanks anyhow.
Guess I`ll be schedualing with a mechanic:sad5:

 

[RedFish]

Don't buy into the corrupt system scenario until you add a can of gas. If the on cycle gets longer you're on the right path. Gas leaks are much more common than compressor failures.
There are a whole lot of places where contaminates come from besides the pumps reed valves too. Interior hose walls rot, etc.. The receiver dryer is supposed to catch all contaminates but it does have a capacity just like any other filter. This is why the orifice has a screen in it. Old school expansion valves contain screens too. Those were small cone shaped screens stacked in any number. I've found 2 and I've found 6. Most of the time the expansion valve itself isn't bad, only the screens need cleaned. We don't clean an orifice tube though. Replace those.

 

[eestatic]

Got a can + gauge, When the compressor cycled off the gauge showed in normal range, 40-45, when cycled on it would drop to about 15lb-. I gave it a little shot and went a little higher when compressor cycled off, getting into the too much range, so I was afraid to add any refrigerant. It would seem like no loss of refrig? I just don`t want to over charge it. I`ve never messed with ac stuff before. Is this normal when comp. cycles off, pressure goes up? Go ahead and keep filling? anybody? sign,clueless:sad5:

When you add freon, its normal for suction side pressure to "bump" up...don't panic.

In an aging system one can often squeeze a few more seasons by periodically topping off system.

Do you have a means to monitor discharge (high-side) pressures?

Charge your system in a cooler part of the day and your systems "head" pressure & suction pressure will not be so high.

Just add a can or two to get compressor from cycling and possibly maintain suction pressure at the 40-45 # range.

Have you ever added any gas before?

 

[Mopar to ya]

Pressure is important. Anyone can add R134a, but are they adding the right amount? And the cans with the pressure dial on them aren't exactly accurate, even if you knew the proper high and low side pressure. Most shops, mine included, charge $20 to check it out and then charge for whatever R134a is used. If you are low, the question is where did it go? Our average non repair R134a check out and fill is around $65. It's well worth it to find if there are any problems and to get it filled to the proper amount.

 

[mopar head]

When you add freon, its normal for suction side pressure to "bump" up...don't panic.

In an aging system one can often squeeze a few more seasons by periodically topping off system.

Do you have a means to monitor discharge (high-side) pressures?

Charge your system in a cooler part of the day and your systems "head" pressure & suction pressure will not be so high.

Just add a can or two to get compressor from cycling and possibly maintain suction pressure at the 40-45 # range.

Have you ever added any gas before?

Thanks, No I`ve never messed with any ac stuff, first time. Truck's been cooling good for 13 years, till now

Pressure is important. Anyone can add R134a, but are they adding the right amount? And the cans with the pressure dial on them aren't exactly accurate, even if you knew the proper high and low side pressure. Most shops, mine included, charge $20 to check it out and then charge for whatever R134a is used. If you are low, the question is where did it go? Our average non repair R134a check out and fill is around $65. It's well worth it to find if there are any problems and to get it filled to the proper amount.

That`s what worried me, I was watching motor week, and ol goss was was talking about weighing+pressures etc. Well today I took the ol gal to town for a bath and the more I drove it the cooler it got, so I slipped by a mechanic I use once in a blue, and he said go ahead and throw a can in it, so I did and she`s blowing cold again, so maybe It`ll last this summer for merayer:
Thanks everybody!

 

[Mopar to ya]

It's not a bad idea to go to the car wash or use your garden hose to clean the debris and crap from between the radiator and condenser. Around here in cottonwood season it is the number one cause of high pressures and inefficient / low cooling on hot days. Gotta keep the air flowing.

 

[tekslk]

I dont no much either but I went to walmart got a can of there stop leak with 134 in it and got five more years out of mine till I traded it, best 20 bucks I ever spent and easy to put in.

 

[toolmanmike]

It's not a bad idea to go to the car wash or use your garden hose to clean the debris and crap from between the radiator and condenser. Around here in cottonwood season it is the number one cause of high pressures and inefficient / low cooling on hot days. Gotta keep the air flowing.

Use the garden hose and please not the pressure wand at the car wash. The high pressure spray will flatten the cooling fins......worse than those pesky cottonwood seeds. Too bad the cottonwoods don't catch a disease. They are the worst trees. tmm

 

[Mopar to ya]

I dont no much either but I went to walmart got a can of there stop leak with 134 in it and got five more years out of mine till I traded it, best 20 bucks I ever spent and easy to put in.

I know that you sign a disclaimer when we work on your AC. If you have stop leak in your system no shop will ever work on it again. It ruins the machines. If you have it and don't tell me, I have the disclaimer and you are buying me a new AC machine. That stuff should be banned.