dj5 Posted August 20, 2019 Share Posted August 20, 2019 sorry if this isn't wanted but my Cherokee is having an issue where its a/c is cycling every few seconds and not blowing cold I hooked up a ac can with a gauge and it goes up to about 60 psi then that's when it cycles again from 0 to 60 and again...and again...and again... ive read I might be too low on Freon but I'm scared to pump more in if its full because I see it go to red then cycle....maybe a bad switch? idk help!!! lol thanks guys I'm in florida and its hotttt, especially in parent pick up line its a 2000 xj 4.0 4x4 btw Link to comment Share on other sites More sharing options...
dj5 Posted August 20, 2019 Author Share Posted August 20, 2019 now I go to check it again and no cycling ac gauge reads red almost 100psi... Link to comment Share on other sites More sharing options...
dj5 Posted August 20, 2019 Author Share Posted August 20, 2019 well I got it fixed, thanks guys lol undercharged system, said f it and went for the charge Link to comment Share on other sites More sharing options...
Big Dan Posted August 20, 2019 Share Posted August 20, 2019 Do you know why the gauges were reading too high if it was under charged? Sent from my Pixel 2 XL using Tapatalk Link to comment Share on other sites More sharing options...
Minuit Posted August 21, 2019 Share Posted August 21, 2019 12 hours ago, dj5 said: well I got it fixed, thanks guys lol undercharged system, said f it and went for the charge You got very lucky. Link to comment Share on other sites More sharing options...
jdog Posted August 21, 2019 Share Posted August 21, 2019 Do you know why the gauges were reading too high if it was under charged? Sent from my Pixel 2 XL using Tapatalk Sounds like it was just one of those gauge on the can and not a full gauge set. So it sounds like it was stagnant but with out a high side I can't be sure. Stock 1988 swb 4.0 ax15 np 231. Link to comment Share on other sites More sharing options...
dj5 Posted August 23, 2019 Author Share Posted August 23, 2019 ok so I have an answer for it all lol my ac compressor has worn out shims, took one out and now all good. the reason the pressure was red is because the compressors clutch plate wasn't engaging because of the air gap after warming up, so if the compressor isn't on, it will always read red on the gauge. figured I would clarify for anyone else this might help Link to comment Share on other sites More sharing options...
Minuit Posted August 23, 2019 Share Posted August 23, 2019 29 minutes ago, dj5 said: ok so I have an answer for it all lol my ac compressor has worn out shims, took one out and now all good. the reason the pressure was red is because the compressors clutch plate wasn't engaging because of the air gap after warming up, so if the compressor isn't on, it will always read red on the gauge. figured I would clarify for anyone else this might help If you're going to keep working on A/C, forget about that stupid can with a gauge on it and get a real set of manifold gauges. To do proper A/C work, you need to know both the LOW and HIGH pressure of the system. You only have a low-side gauge right now. Any data that does not include BOTH pressures at any given time is pretty much useless. When someone asks an A/C question on here I tend to ignore any measurements taken with one of those stupid recharge kits. They're usually pretty far off of the true reading anyway, since they're cheap junk. A low pressure gauge only, especially one from a recharge can, is not an acceptable diagnostic tool for A/C work. You currently have no idea what your high side pressure is. It's probably just fine, but what if it isn't? Clutch air gap should be between 16 and 31 thousandths of an inch, if anyone is curious. What you're seeing when you say the gauge goes into the red is the static pressure of the system when it isn't running. For R-134a, the static pressure happens to be roughly equal to the temperature in Fahrenheit inside the system. If the truck has been off for long, that's roughly the ambient temperature. All that static pressure tells you is whether or not there is some amount of liquid refrigerant inside the system. There may be a teaspoon of it in there or it may be stuffed to the gills. There is one correct number that this should be for a given temperature. If it's not that, you either have an empty system (or close enough) or contamination. When you said it was "almost 100", I'm betting it was somewhere around 100 degrees outside, right? When the compressor kicks on, it sucks refrigerant out of the low side of the system and squeezes it against its will into the high side, so the low side pressure will drop and the high side will climb. If you know the pressures on both sides of the system, you can tell quite a bit about how well your system is running. The pre-'97 XJs and MJs have a very different system that basically NEVER short-cycles. Refrigerant flow is regulated by an expansion valve, and compressor duty cycle is controlled by a thermostat in the evaporator. '91-'96 systems, and I'm pretty sure the earlier ones too, have no true low-side cutoff switch. One big downside - it also has this funny little feature where it will let the compressor pull a vacuum on the low side without skipping a beat in just the right circumstance. Link to comment Share on other sites More sharing options...
dj5 Posted August 24, 2019 Author Share Posted August 24, 2019 i do need to get real gauges, but the dummy gauge seemed to work okay for now and i seemed to have found the issue i have other expenses on the xj I'm worrying about right now so ac was just a nice bonus to get going for only $20, but yes you were exactly right about the air temp being around 100 degrees outside here in FL. Link to comment Share on other sites More sharing options...
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