While I was under the hood fidlding with the IAC I decided to take a look at the (non-operational) A/C system as well. I'm pretty new to A/C systems, so bear with me, but this is what I've gathered so far....
1) When the car is running and I turn on the A/C, the compressor kicks on. It only will stay on for a few seconds at a time though, and then it turns back off again, and a few seconds later, repeats the cycle.
2) I pressed the little valve in the line above the passenger side wheel well (low-side I think?!?!) and got sprayed in the face with a NEON-GREEN/YELLOW liquid... (okay actually it sprayed and the wind BLEW it in my face... I wasn't that dumb to stick my face above the nozzle haha)
3) None of the lines feel at all cold. Several of them are hot (but most of the ones I felt were right above the engine), and the line I pressed the nozzle on is just about luke warm.
So I guess this is good... meaning the system is holding pressure if I got sprayed right? What is the neon green/yellow fluid inside? Whatever it is, is it compatible with the new r-134a stuff that you can get at the autoparts stores in the can?! I'm assuming that none of the lines got cold because the compressor wasn't on long enough, and wouldn't stay on long enough to see. Is that an accurate assumption? Would low fluid pressure cause the compressor to not stay on?! If not, what do I need to check? I guess really what I'm hoping for here is a bit of a diagnostic from some of you more experienced A/C servicers, or what my next step should be in getting her going again. Any ideas?! Thanks!
My compressor clutch cycled on/off every 5 to 10 seconds when it was low on Freon. The 1994 jeep uses R134a as listed on the sticker located on the top of the radiator. Mine was cool but no way cold and on 95 degree days it did almost nothing.
I added about half a can (until I got 45 psig) of this stuff. Now she runs cold and the compressor does not cycle.
You're short cycling. Well, to be exact, your compressor is...
Low on refrigerant, and it's probably R134a, (you can be certain by the connectors, since R134 and R12 use different connectors, so you can't (easily) put the wrong stuff in...
The neon stuff is the oil, and it needs to stay.
Buy a can of R-134a, add about half and see if the system starts to work. You can get a can with a built-in pressure gague that will tell you how much pressure there is in your system so that you don't over-fill the system.
Thanks for the info guys. I went and picked up a can at my local auto store, and went to put some in, but now I'm confused... The can says to turn the car on, turn the A/C up to max, and monitor the pressure of the system as you add fluid, as not to go over 45psig. However, when I hook the nozzle with the A/C on full, the pressure gauge starts at 25, then the compressor kicks in and it raises until it hits about 65 (which is supposedly the start of the danger zone according to the can) and then the compressor shuts off for a few seconds, then starts the cycle again at 25. Am I doing this wrong? SHould I not be doing this with the engine running? Are you guys saying 45psi with the system off? I didn't want to just add some and overcharge the system to the point of danger if it ends up being something else. What do you guys think?! Thanks!
Once you add some, you must close the valve (by screwing in the pressure gage clockwise). Then take that reading. It will be lower than the direct reading when charging it. Then if needed open the valve (counter-clockwise) to let the Freon flow. Re-check.
Once you add some, you must close the valve (by screwing in the pressure gage clockwise). Then take that reading. It will be lower than the direct reading when charging it. Then if needed open the valve (counter-clockwise) to let the Freon flow. Re-check.
Sorry, but I'm a little bit confused by the terminology here... once I add some r134a, I have to close what valve? And screw what in? The pressure gauge I got has a quick release to hook it up to the valve in the system (so no screwing involved), and then connects to the bottle of fluid. The gauge itself does not turn/screw either. I haven't put anything into the system at all yet... all I've done is hook up the gauge and take the reading... so I assume this is the same thing as what you are talking about when you say with the valve closed?!?! If so, is my reading not normal, or does it suggest a different problem than low fluid? Like I said, I'm just a bit skeptical about putting more fluid in the system if that's not the problem.... but I have no idea what to think with a reading that ranged from 25-65 repeatedly. Am I doing this right by checking with the A/C on max? Is this normal behavior for a "short cycling compressor"?! Should I just forget the readings and put some more fluid in hoping it stops the short cycling and gives me a solid reading? Thanks.
Sorry, but I'm a little bit confused by the terminology here... once I add some r134a, I have to close what valve? And screw what in? The pressure gauge I got has a quick release to hook it up to the valve in the system (so no screwing involved), and then connects to the bottle of fluid. The gauge itself does not turn/screw either. I haven't put anything into the system at all yet... all I've done is hook up the gauge and take the reading... so I assume this is the same thing as what you are talking about when you say with the valve closed?!?! If so, is my reading not normal, or does it suggest a different problem than low fluid? Like I said, I'm just a bit skeptical about putting more fluid in the system if that's not the problem.... but I have no idea what to think with a reading that ranged from 25-65 repeatedly. Am I doing this right by checking with the A/C on max? Is this normal behavior for a "short cycling compressor"?! Should I just forget the readings and put some more fluid in hoping it stops the short cycling and gives me a solid reading? Thanks.
When you connected, and turned the system on you got 65 while the compressor was running, and 25 when it wasn't? And you haven't opened the valve on the can to allow any R134A to flow into the system yet. Is this correct?
If so... You're WAY OVER PRESSURE. The 94 and 95 Grand Cherokee's A/C systems should have an operating pressure of between 32 and 41 on the low side, and 200 to 260 on the high side.
If it were me, I'd hook a full set of manifold gagues to it before I did anything else, and watch the readings on both sides to make sure that there's not a blockage, or something else going on first. See if your parts store "loans" them out for a deposit, like AutoZone does here.
If you are, in fact, simply over-pressure, you'll need to release pressure from the system until pressure is back where it should be.
Sorry, but I'm a little bit confused by the terminology here... once I add some r134a, I have to close what valve? And screw what in? The pressure gauge I got has a quick release to hook it up to the valve in the system (so no screwing involved), and then connects to the bottle of fluid. The gauge itself does not turn/screw either. I haven't put anything into the system at all yet... all I've done is hook up the gauge and take the reading... so I assume this is the same thing as what you are talking about when you say with the valve closed?!?! If so, is my reading not normal, or does it suggest a different problem than low fluid? Like I said, I'm just a bit skeptical about putting more fluid in the system if that's not the problem.... but I have no idea what to think with a reading that ranged from 25-65 repeatedly. Am I doing this right by checking with the A/C on max? Is this normal behavior for a "short cycling compressor"?! Should I just forget the readings and put some more fluid in hoping it stops the short cycling and gives me a solid reading? Thanks.
OK you have a different refill kit then you do. My pressure gage screws into the Freon can to puncture the seal. So the valve in this case is the pressure gage.
When you connected, and turned the system on you got 65 while the compressor was running, and 25 when it wasn't? And you haven't opened the valve on the can to allow any R134A to flow into the system yet. Is this correct?
If so... You're WAY OVER PRESSURE. The 94 and 95 Grand Cherokee's A/C systems should have an operating pressure of between 32 and 41 on the low side, and 200 to 260 on the high side.
If it were me, I'd hook a full set of manifold gagues to it before I did anything else, and watch the readings on both sides to make sure that there's not a blockage, or something else going on first. See if your parts store "loans" them out for a deposit, like AutoZone does here.
If you are, in fact, simply over-pressure, you'll need to release pressure from the system until pressure is back where it should be.
dbtolman, yes and no. Yes, I have NOT opened the valve to add any r134a at this point. Yes, the pressure reads between 25 and 65. But, NO it's not just 65 while on, and 25 while off. When I hook up the gauge theres a cycle of the pressure reading 25, then rising linearly with time over a few seconds until it reaches 65, then kicks the compressor off for a couple seconds, then starts over again at 25. It's not like as soon as the compressor kicks on it's at 65 psi... it takes a few seconds for the pressure to rise to that, and then kick off. Granted I don't really have any experiance with A/C systems, but my first intuition was "hmm... seems like the system is gaining too much pressure, and kicking the compressor off (kind of like a safety)... I wonder if the system is clogged somewhere and not flowing, just causing a constant rise in pressure until it kicks back off?!?"
So, I guess that would lead me to these manifold gauges you are talking about. How would I go about using them to determine if there is a blockage in the system, and how do the work any differently than the gauge that I have for measuring the pressure?! If it is a blockage in the system, how would I go about finding where it is, and removing it, so that I can get the refridgerant flowing again so I can use my A/C?! Thanks.
I have a similar AC pressure problem on my '94. My tech told me what your last post said, system is plugged causing quick, high pressure and little to no AC cooling. He said that small shavings from the compressor piston eventually wear causing the system to plug. Suggested several parts that run $5-600.
I saw your post awhile ago. I couldn't remember my password to get back on, so had to reset it, took a couple of days. Yeah, and I'm lazy...
Anyway, I read your post, and my diagnosis is that you're mixing up the compressor bieng on and off.
To say that the compressor kicks on, brings the low side pressure up to 65, and shuts off doesn't really make any sense. On the other hand, having the compressor on, bringing the pressure DOWN on the low side to 25, then clicking off and having the pressure rise makes perfect sense, and is exactly what the system is supposed to do. Therefore, when the compressor clicks on and off, I think you just have on and off confused.
If my diagnosis is correct, you're simply low on refrigerant. When the compressor is "on" and pulling the low side pressure down (from 65 to 25), add a little R134a. Do this until the compressor stops cycling, and then continue to fill based on the method you've selected (fill to 45 psi, fill based on sight glass, fill till it works..... etc).
Hope this helps.
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Jeep Enthusiast Forums
18.5M posts
726.8K members
Since 2000
A forum community dedicated to all jeep owners and enthusiasts. Come join the discussion about performance, engine swaps, modifications, classifieds, troubleshooting, maintenance, and more!