A/C compressor cycles.. won't stay engaged

My what warm weather we've been having...

and to say the least how nice it might be to have a 94GC w/ 4.0 that has a working ac but alas it is not to be. My ladyfriend has to drive in this unbearable heat. She tells me that she doesn't like it so I try to recharge the system. I started the jeep up and allowed it to run with ac engaged. While this is happening I go to the low pressure side of the ac line and push in the shrader valve and leak out the old 134a. I noticed that the compressor comes on for about 2secs. and then disengages. I believed that that meant there wasn't enough 134a in the system and it needed a recharge but after attempting to put in 1 can of the stuff it still kept up the cycling (on for 2secs. and then off). I watched the clutch catch and then disengage. I even noticed that when the compressor was engaged for 2 seconds the can of 134a would get colder. Seems like some of the 134a got in the lines but the compressor just wont stay on. This ofcourse won't cool the air in my ladyfriend's jeep which makes aforementioned ladyfriend kinda grumpy. She's not nearly as friendly and that can make for a long night...

I believe I have the same issue. Any help will be greatly appreciated!

From what I've come to find out from a friend in the auto repair business is that I had not allowed enough time for the can of 134a to be 'sucked' into the system. The jeep has to remain running with the ac on. The compressor will continue to cycle, engaging the clutch and sucking more coolant into the system. The cycles should get longer and longer until the clutch stays engaged. :banghead: Who knew? I sure didn't but this is, afterall, the first system I've ever recharged...

Took me two full cans yesterday to get it full enough to keep the compressor from cycling.

Just wait it out. Every time the compressor cycles it will suck some out of the can. There's a way to jump a connector if your compressor won't cycle at all, it's detailed in the Haynes manual. That will force the compressor to spin and suck the cool juice out, but I didn't see the need to do that.

It only took all of 15 min to put the two cans in and bring the system back to functional.

When my woman got home today I went right to work... on the jeep. I hooked up the half a can I had left from monkeyin' around yesterday. The can says to leave it upright while it fills but I turned it upside down and noticed immediately the cycling period began increasing. When I finished off the half a can I added a 2nd full can and the air inside the cabin began cooling down. The compressor stayed on as well, continiously. I'm thinking of trying for one more can and then letting it go until next summer but as of right now my woman thinks I'm a genuine HE-RO. It's blowing cooler but I do think it gets colder.

I'm thinking of trying for one more can and then letting it go until next summer but as of right now my woman thinks I'm a genuine HE-RO. It's blowing cooler but I do think it gets colder.
So does that mean you can get a woman hot by cooling her down? :)
I would stick a pencil type thermometer in one of the AC vents and watch the temperature if you plan to add more refrigerant...it's possible to overfill the system.

If you ever need to 'hotwire' your 12 volts to the ac clutch just pull the pressure switch off the top of the accumulator and stick a short loop of single strand, insulated wire into each end of the sockets on the harness you unplugged. Just be careful in doing so. There is a reason the pressure switch cuts off the juice when the system pressure gets too low. (The freon suspends the oil lubricant particles which keep the pump from siezing up.) Don't they still sell the pressure gauge kits at stores to take the guesswork out? both my vehicles are still running R12 so I don't deal with them since I can't get my hands on the good stuf anymore...

I once put 4 1/2 cans into an empty system, and it worked fine. The system operates on pressure, not volume of coolant; so unless you're using some special high pressure system to put it into the system you should be ok with the cans and not overpressurizing it.

This seems to be a popular complaint. I have this trouble. Pressure gage says it has plenty of refrigerant but still cycles on and off, a manual check of codes brought up '33' "Airconditioning Clutch relay circut. An open or shorted condition detected in the Airconditioning Clutch relay circut." Anyone know where to start to search for this? Is there a way to check this with a meter?:banghead:

I once put 4 1/2 cans into an empty system, and it worked fine. The system operates on pressure, not volume of coolant; so unless you're using some special high pressure system to put it into the system you should be ok with the cans and not overpressurizing it.
You can absolutely overfill the system - in this case the high pressure is the pressurized can of coolant. You're only guessing without a gauge. At least use a thermometer so you can detect when its becoming overfilled.

You can absolutely overfill the system - in this case the high pressure is the pressurized can of coolant. You're only guessing without a gauge. At least use a thermometer so you can detect when its becoming overfilled.

True enough, and I oversimplified....sorry for any confusion.

This seems to be a popular complaint. I have this trouble. Pressure gage says it has plenty of refrigerant but still cycles on and off, a manual check of codes brought up '33' "Airconditioning Clutch relay circut. An open or shorted condition detected in the Airconditioning Clutch relay circut." Anyone know where to start to search for this? Is there a way to check this with a meter?:banghead:
If you're absolutely sure the pressure checks out ok, you can use the "hot wire" method described above, in which case you'll most likely find a defective pressure sensor.
And as noted above, if there is not sufficient coolant in the system when doing this, you will fry the compressor.
It's also a good idea to add some lubricant if you have to re-charge the AC.

If you're absolutely sure the pressure checks out ok, you can use the "hot wire" method described above, in which case you'll most likely find a defective pressure sensor.
And as noted above, if there is not sufficient coolant in the system when doing this, you will fry the compressor.
It's also a good idea to add some lubricant if you have to re-charge the AC.

Bob D is right. All A/C systems suspend the lubricant in the freon. At most auto part stores you can buy a 134a and oil charge mix. I highly recommend this if your system is almost empty. Also check all your fittings for signs of oil, since the oil is suspended in the freon the oil comes out with it and attracts dirt. Under the hood on the A/C information sticker it will tell you how much your system holds and what type of freon it is. I just charged my 96 GCL and it said 28ozs is a full charge. Also if you research on line you should be able to find a temperature/pressure chart which will give you an idea if your system is over/under charged.

So which switch is the low pressure port on a 93 4.0. Any pics would be great

My what warm weather we've been having...

and to say the least how nice it might be to have a 94GC w/ 4.0 that has a working ac but alas it is not to be. My ladyfriend has to drive in this unbearable heat. She tells me that she doesn't like it so I try to recharge the system. I started the jeep up and allowed it to run with ac engaged. While this is happening I go to the low pressure side of the ac line and push in the shrader valve and leak out the old 134a. I noticed that the compressor comes on for about 2secs. and then disengages. I believed that that meant there wasn't enough 134a in the system and it needed a recharge but after attempting to put in 1 can of the stuff it still kept up the cycling (on for 2secs. and then off). I watched the clutch catch and then disengage. I even noticed that when the compressor was engaged for 2 seconds the can of 134a would get colder. Seems like some of the 134a got in the lines but the compressor just wont stay on. This ofcourse won't cool the air in my ladyfriend's jeep which makes aforementioned ladyfriend kinda grumpy. She's not nearly as friendly and that can make for a long night...

You need a low and high side gauge to do it safe and right.
Wal Mart DEATH KITS

You cannot properly and safely recharge an air condition system with them.

The one side stop and go gauge does not tell you what your system is doing or is over charged or undercharged.
A overcharged or malfunction air condition system can reach over 500 lbs of pressure.
Enough to blow up that can or system and freeze you at first and the burn you or blind you and if any propane /butane in there blow and light you up.

The stop leak crap and who knows what kind of oil in the kits there will stop your system for sure.
Just like pouring super glue in it.
And some kits even contain freon with a butane mixer.
Good for a big blast.

If you are going to do it do it right and safe.
Here is what you need to start with.
http://www.ackits.com/merchant2/merchant.mvc?Screen=PROD&Store_Code=AMA&Product_Code=66773

In the older days you could just throw in a can and go.
But over the years just adding freon is getting harder to do.
Newer systems have to have the correct amount of freon down to the ounces.
Most will need pumped down and vacuumed down and the right and amount of oil and a set amount freon charge installed to get the air to cool right and the system to last.
If an air condition is low there is usually a leak that needs fixed and also a lose of lubricating oil from system.
Also air and moisture enters a low system
If you are going to try to do it get the proper type air condition gauge set with the low and high side gauges.
Hook up the gauges and get a reading with compressor running at idle and at 2000 rpm on the high and low side.
Post back pressure reading and we can help you.
MT

never turn the can upside down and allow the liquid to run into the system. it does't evaporate into gas in the pressurized lines as easily. can cause bad pressure readings while rechargeing. I use the death kits and ussually don't use the gages because they are cheap and not accurate. 3 different gages said my system was over pressureized but still took 2 1/2 cans. took to shop and was told it was still low. MT's right. spend the money on good gages to do it right. Ordered mine tonight.

So whats the correct pressure were looking for here. Im Gonna do a recharge (attempt) tonite. Dont wanna overfill anything.

So whats the correct pressure were looking for here. Im Gonna do a recharge (attempt) tonite. Dont wanna overfill anything.


As said death kits and recharges is not the proper way to recharge a AC system.

Wal Mart DEATH KITS

You cannot properly and safely recharge an air condition system with them.

The one side stop and go gauge does not tell you what your system is doing or is over charged or undercharged.
A overcharged or malfunction air condition system can reach over 500 lbs of pressure.
Enough to blow up that can or system and freeze you at first and the burn you or blind you and if any propane /butane in there blow and light you up.

The stop leak crap and who knows what kind of oil in the kits there will stop your system for sure.
Just like pouring super glue in it.
And some kits even contain freon with a butane mixer.
Good for a big blast.

If you are going to do it do it right and safe.
Here is what you need to start with.
http://www.ackits.com/merchant2/merchant.mvc?Screen=PROD&Store_Code=AMA&Product_Code=66773

In the older days you could just throw in a can and go.
But over the years just adding freon is getting harder to do.
Newer systems have to have the correct amount of freon down to the ounces.
Most will need pumped down and vacuumed down and the right and amount of oil and a set amount freon charge installed to get the air to cool right and the system to last.
If an air condition is low there is usually a leak that needs fixed and also a lose of lubricating oil from system.
Also air and moisture enters a low system
If you are going to try to do it get the proper type air condition gauge set with the low and high side gauges.
Hook up the gauges and get a reading with compressor running at idle and at 2000 rpm on the high and low side.
Post back pressure reading and we can help you.
MT


To do a proper recharge you need to pump it out and check oil and pull a vacume on it and install the correct set charge of freon for your system.

Gauge reading of 30 lbs low side and 150-250 lbs high side at 2000 rpm with compresser running is the correct pressure you should look for.
With a vent tempture of 35-40 degrees.
Gauges can not tell the exact charge but will give you a good idea if system is working right.
MT