Hello there! im new here and unfortunately i have to start it off with something negative. I recently purchased a 2001 XJ and in the ad it said the ac system didn't work.. i said hmm okay maybe this guy just doesn't know about Freon. i get the jeep home and the first thing i do is open the hood to tackle this ac problem. i went out and bought a brand new can of Freon and hooked the Gage up to the low pressure port to fill the ac, which if im correct its the port closest to the fire wall. when i hooked the gauge up it instantly read that it was wayyyyy overcharged. and the gauge was fluctuating (meaning the clutch would be off till it got up to pressure then the clutch would turn on for one or two seconds and the pressure would tank. repeat repeat) so the next step i did was google it. i saw somebody had a quick fix saying to bleed the ac lines down till it was stable. which i then did, and when stable the clutch didn't move at all. so i said maybe its bad Freon, maybe the gentleman had no ac for a long long time. i proceeded to add Freon and i got one 10 second pull of the can before it read that it was in middle of the "filled zone" after checking my ac to see if i had fixed the problem, the gauge and clutch started fluctuating again. i am beyond confused. i dont know if its a bad sensor, bad clutch, bad compressor. after letting the car run for about 10-15 minutes i check the piping and it was more warm then cold.


any suggestions at all please comment or shoot me a message any help would be so much appreciated.

Thanks.

 

If the AC system was nonfunctional, then it most likely had lost the vacuum. Once the vacuum is lost for any extended period of time you need to start over with a new receiver/drier, vacuum the system and then refill with the proper amount of R134. Without a way to pull a vacuum and ensure the system does not have leaks and a manifold gauge set, you really won't be able to do much. If you want to try doing this yourself, you will need to read up on the Cherokee AC system. Get all the refrigerant out, get a seal kit and replace all the seals, then check for a leak by pulling a vacuum. Here is a chart with refrigerant and oil amounts: https://www.techchoiceparts.com/refr...apacities/jeep. Here is a troubleshooting chart for low and high side gauge readings: http://rechargeac.com/how-to/ac-system-pressure-chart.

 

thankyou!

 

It's normal for the low side pressure to start high, and slowly get pulled down until the low pressure switch cuts it off as as the compressor runs. Rapid cycling however of the pressure like that means it's low on freon (ie the low side gets emptied out very quickly). The guages on those cheap cans aren't that accurate, and the color markings don't account for ambient temperature. Since it still had some pressure, it's probably just got a very slow leak and needs freon added. Being empty, I'd probably just add a coule cans and see if it cycles normally and gets cool.

 

Hold everything, was that port on the large line or small one?

 

If he just bought a can off the shelf then he'd only be able to connect to the low side.

 

You really need a full gauge set to monitor what's going on. At best you're only seeing half the story with the cheapo low-side gauge on the can. There are plenty of youtube videos out there showing how to use a gauge set. Use only pure R134a with no sealers, those can really mess up your AC system. (Best local prices are usually at Wal-Mart, about $5/can.)

https://www.harborfreight.com/ac-r134a-manifold-gauge-set-60806.html

 

This is the best advice you will get. I have the Harbor freight gauges and it only cost me about 40-50 bucks with coupon if i remember right. You NEED to see the high and low side pressures while you are charging the system. Also while you are there, get the vacuum pump so you can draw down and properly remove all the moisture from the system before you charge it.

The good news is the compressor seems to be working, so that's one less thing to replace. If you can remove all the freon from the system, then pull a vacuum on it and let it sit. Hopefully the system will hold pressure indicating no leaks. As soon as you have verified that there are no leaks, then you can replace the receiver dryer and pull a vacuum again to make sure there is no water in the system. If you wanted to, you could flush the system, but assuming it hasn't had a leak, you could probably get away without doing it, since you are not really changing many parts. Once it is vacuumed out, then you can properly charge it with the amount of oil and refrigerant specified, usually a sticker under the hood will tell you. Don't get any of the fancy R134a with sealants, etc. etc. Dupont suva (i think) can usually be had relatively cheap on amazon. Then you should be good to go.

 

Not to be that guy but I would suggest not posting up that you intentionally released refrigerant into the atmosphere. You’ll get slapped with a fine by the EPA.

with that said, cycling compressor means the pressures are off, if you watch the low side and see the gauge peg empty and rise again after the clutch shuts off, you have low refrigerant.

keep adding until the compressor no longer cycles, if air was in the system, get the system evacuated at a shop and make sure the system is under vacuum for a minimum of 20 minutes. Fill to specs in service manual, 20 OZ of R134a (the system may be old still and need a retrofit from R12).

once fill is completed, run the vehicle and air conditioning with a thermometer in the center vent. with the ac on high, maintain engine speed to 1500-2000 rpm, and record the temperature after 10 mins. This is called a AC performance test, ambient air will affect the output temp but you see under 80F even in 120F weather if the system is working properly.

goodluck

 

That's right. You should also have a box fan pointed into the radiator. If you don't have some air movement you won't get as good of heat trasfer (at the condenser) and therefore your discharge temps will read lower than they would be with some air movement.

 

Very true about not venting to the atmosphere, but I thought he said it was empty, then he only put a little bit in. It is not good to vent to the atmosphere, and I usually don't do it myself.