So, sad day. Friday my 2000 xj died. Radiator went out, apparently blowing a cylinder or something like that. Cost got over $1000 and climbing, so did what any good xj owner would do and bought another one.

So, on the one I am getting today, he told me the AC was bad and needed a new compressor. The problem is, how do I know if that is right and if I should replace more than that. What am I looking for to diagnose it is definitely the compressor and not something else? I see there are some instructions on how to replace that I will eventually follow and then take it to get evacuated if needed and charged. Just don't want to dump too much in to a 17 yr old jeep if I don't have to, but will need air conditioning.

 

Loosen the belt and see if you can spin the pulley on the compressor by hand.

After that, put the belt back on and see if there is enough refrigerant in the system to make engage the clutch when you turn the AC on. If the clutch engages and you hear the belt start to squeal, you know your compressor is bad.

If you verify that there's plenty of refrigerant in the system and the clutch isn't kicking on, the clutch itself may be bad... which would be a lot cheaper than replacing the compressor.

If there isn't enough refr in the system, find some refrigerant at the autoparts store with the fluorescent tracking dye. Sometimes you can find a kit that comes with a little black light and the special glasses to see the leak.

 

Thanks. I didn't loosen belt, but it engages and no squeal. I'll buy some refrigerant with dye tomorrow and try that. A little hot in there right now.

Also, with everything off, I notice hot air blowing on my foot. It's 87 outside, so not sure if it is hot air from outside or something else. Checked and heat does work.

 

At least get one of the R-134 cans that have the low pressure side gauge. Far less than ideal to diagnose the AC system but better than just adding some refrigerant. Ideally, you want . gauge set that reds high side pressure and low side pressure. If the system is working correctly with the correct amount of refrigerant, those cans with just the low side gauge can get you close enough. If the system has lost all refrigerant and has pulled in air then you'll need to fix the leak, replace the drier, evacuate and then charge/figure out if the compressor is bad. It is much more common for the clutch to go bad vs. compressor to go bad.
You can check the clutch for engagement by putting 12 volts to the single wire connector to the compressor. You should see the clutch plate move in and out depending on if the wire has 12V or not. You will her it click too.

 

It can be any part of the ac system wrong or leaking.Just pray its not the evaporator which is in the heater box under the dash and a pain to replace.

 

Should I grab a can of r134 or just go ahead and take it somewhere. if I take it somewhere to get checked, how much for a diagnostic, how long will it take and what type of places can do it - jiffy lube, mechanic, other specialty places?

 

If the clutch is engaging the pressure is probably close to OK or the pressure switch would not allow the clutch to engage. That, and the fact that it is blowing hot air on your feet makes me wonder if the AC is ok but the blend door is not doing it's thing for some reason.

with the AC running see if the metal line coming thru the firewall (on the engine compartment side)from the evaporator is cold. If it is the AC is probably not the problem

 

Look around on here, there is a thread regarding the removal of a shim on the ac clutch which solved my problem over three years back. Also a youtube video.

 

As has been said, you need to get some R-134 with dye. I also suggest getting some that has the stop-leak in it. I know everyone says it's crap but I did some *significant* research on the topic recently for my 1995 F-150 that I bought. It's not the same as the stuff from 20 years ago. I work with PhD chemists and talked to *them* about it. The new stuff only reacts only when it comes in contact with the atmosphere, other than that it's non-reactive. After doing all that I said screw it and threw some in my truck last spring. The air is still blowing so cold I have to turn it down after a few mins.

*Granted* I checked my system and I was able to pretty much hold vacuum so I had a very small leak somewhere.

Also, it's a good bet that if you have a leak that you've lost some of the PAG oil. I like to look for refrigerant that has PAG oil in it, though I wasn't able to find any last time. I did buy a small PAG oil bottle (pressurized) and put in about 1/3 of it just for safety's sake.

But, saying all that...your very best bet it is to put the dyed refrigerant in. If it get's cool then you know the system is functioning, but loosing refrigerant (and oil!). So after it stops cooling, then use the UV light and try to locate where it's leaking from. Replace required parts (after it's been depressurized at a proper AC recycling location). Rent/borrow/buy a set of AC gauges and a vacuum pump, vacuum down for about an hour or so, make sure it holds vacuum. Then fill with refrigerant. Remember that an AC compressor won't kick on with too low of refrigerant as a protective measure.

Good luck man!

-Matt

 

Hey guys, hoping to revive this thread in order for someone to help me out with my busted AC.

Like most people, my AC blows hot air. My compressor kicks in, but it's always low on freon so I know I have a large leak. I got the UV dye freon and no leaks are visible at all(really hoping its not the evaporator). The biggest issue, and my question really, is that when I charge the AC with the auto zone canister, the needle moves up and down as the compressor kicks in. I'm pretty sure that is not supposed to happen, possibly a leaky valve at the port? I have no clue.

I have a video I'm trying to upload, but basically the needle drops when the compressor kicks in, and moves back up when it turns off. The compressor seems to be working fine, and I can see it spin, but it doesn't stay on.

 

I'm no AC expert, but I'm pretty sure when the compressor kicks on and off, the pressure is going to fluctuate. I havent had to do AC work on my XJ, but my Cummins had an AC issue and when I used the AC fix-it can with the gauge, it would move around as the compressor was coming on and off. My issue turned out to be the clutch, and it wasnt engaging enough to move the refrigerant I guess. I removed the compressor and changed the clutch in about an hour, and then took it to get recharged. Problem fixed.

 

The pressure changing is normal. The compressor kicks on and sucks the low side down until it the low pressure cutoff. It kicks on after the pressure comes back up above a certain pressure (high than the cutoff on the way down). How fast it cycles is an indicator of how much freon you've got in the system. Cycling more than 10-times a minute with the a/c on full blast usually means undercharged.

 

I need to figure out how to upload a video so you can see. Basically I’ll charge it so it reaches about 50psi but the compressor kicks in about every 5 seconds no matter how much I charge it. The compressor will stay on for about 5 seconds, the pressure will drop to about 5psi, the compressor shuts off and the needle moves back up and the compressor kicks in when the needle is at about 50psi. The needle never stays at an exact spot, is always moving up and down

 

Sounds very under-filled to me.

 

50psi is right before it hits the red where it’s overfilled. I know it all leaked out fast, but would it still be under filled if it’s reaching 50? Also with the IV dye I can’t find any leaks