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Discussion Starter · #1 ·
Not too long ago, maybe a month ago, I posted about having trouble with the a/c on my 1996 Cherokee Country 4.0. with an R134a system. At that time, I evacuated the refrigerant from the system, pulled a vacuum somewhere between 27 and 29inHg for no less than 30 minutes which held for at least another 30 minutes, recharged the system, and then had cold a/c. I charged the system watching the manifold gauges and the sight glass. The sight glass appeared as though a streaming fog was moving across it. To the best of my knowledge, the parts are all original.

Late last week, I got in to go somewhere and even though it wasn't all that hot outside, I felt hot and switched on the air. It did well for a few minutes, but then the air coming out of the vents became less cool. I hooked it up to the gauges and looked at the sight glass. I could see refrigerant moving across the glass, but it was more bubbly and less foggy looking, and the pressure on both gauges was quite low. I decided to see what would happen if I tried to add some R134a to the system. It seemed reluctant to take it. I could still see movement in the sight glass, but the can wasn't getting all that cold like it normally does when the refrigerant leaves it. But a change came when the high side gauge started steadily moving up, and then the low side started pulling a small vacuum. I stopped trying to add refrigerant when the high side hit 225 and the low side was still pulling a vacuum. It happened pretty fast.

Someone told me that this sort of thing can be caused by a leak that's allowing outside air to enter the system, which freezes due to its relative humidity, which mimics the symptoms of an obstruction in the a/c plumbing. Does this sound right? I figure that if the compressor had failed, I wouldn't have been able to see refrigerant moving through the sight glass, so I would like to think that's not the issue. Can the compressor shaft seals fail and the compressor still appear to be working?

We haven't yet had any of those 90+deg days with muggy levels of humidity, but they're coming and I would like for the Jeep to have working a/c when they do. Any advice would be appreciated.

Thank you,
-William
 

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I agree with the leak diagnosis. Larger bubbles in the site glass mean that there is not as much liquid refrigerant coming off the condenser coil. When this happens, the evap coil becomes colder and ice forms on it when condensation is pulled out of the air. You will probably notice that when you turn it on again that it will work for awhile and then over time it won't work at all due to the leak
 

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Discussion Starter · #3 ·
I agree with the leak diagnosis. Larger bubbles in the site glass mean that there is not as much liquid refrigerant coming off the condenser coil. When this happens, the evap coil becomes colder and ice forms on it when condensation is pulled out of the air. You will probably notice that when you turn it on again that it will work for awhile and then over time it won't work at all due to the leak
Well, it doesn't work very well now even when I first switch it on. It is cooler than ambient air, but not by much. Not enough to make you feel cool inside the car, and it just seems to get more tepid. I don't want to take it anywhere because around here, that's $1000 just to get started on an a/c job. I'm not afraid to wrench on something. Be careful, follow any instructions, and exercise common sense, you know?
I just wish I knew what would be leaking in such a way that it would allow outside air to enter the system. That would keep me from having to throw parts it it. Rock Auto has a kit to change out a great deal of the parts in the a/c for new that's not too terrible on the price. But doing all the work takes alot of time when you can't dedicate a day to getting it done.
 

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I don't agree with the idea of outside contaminating the refrigerant. As I said, the extra bubbles is lack of liquid refrigerant. It is time to get some dye and put it in and use a UV light to look for your leak. If you cannot find one visible outside, then you will likely have a evap core leak. Granted that is a real pain, but not uncommon
 

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Discussion Starter · #5 ·
I just went out to have a look at it. Started the Jeep, set the air to Max at full speed fan. Low side still appears to be pulling a vacuum.

I was able to get it to take some R134a with dye in it.

Something I noticed is that there are two hoses connected to the expansion valve. The low pressure hose (fat side), and what appears to be a high pressure line that runs down to the receiver/dryer (skinny side). The skinny side of the valve was covered in a thin layer of frost.

Is this indicative of an issue with the expansion valve?
 

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If you are getting ice, then it is running too cold, which is what happens when it is slightly low. If it leaks more, then the temp will rise on the low side
 

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Discussion Starter · #7 ·
Think I'm going to take it somewhere and have them evacuate, pull a vacuum, and then charge to the factory-specified amount of R134a. That will give me a better benchmark to work with.
 

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OK, let us know how it goes
 

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Discussion Starter · #9 · (Edited)
I haven't picked it up yet, but they did what I asked them to do and told me that it was cooling. They said they suspect a leak in the evaporator core. My thoughts are maybe, maybe not. It wouldn't have been able to pull and hold a vacuum back when I did that, but that was at least three weeks ago, if not longer. Anything could have happened since then. So, I'll see what happens when I drive it. Been in the low 80s the last couple of days around here.

Edit: It was blowing very cool when I picked it up right around dusk. Temp was still in the high 70s at the least and quite muggy as a rain shower had just passed through.
 

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Hmm...If I were you, I would take this situation seriously because, for me, there is nothing more serious than cleaning the air conditioner. This can sometimes cause some serious problems. That's why I take my device to marvellous.sg as often as possible for a total cleaning and inspection. It helps a lot and prevents many malfunctions, so I suggest you take the same opportunity to be more knowledgeable about your air conditioner. Use it wisely.
 
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