A/C System issues, done diagnosis, need pro advice...

So here is my situation. 93 XJ with fittings on compressor for R134a.

I had been futzing around in my engine bay and kinked an AC hose years ago. I just recently got around to fixing that, it has been hot and I've wanted the 'luxury' of A/C again. Ended up replacing both hoses to and from the condensor, the condensor itself, drier/receiver, expansion valve, and used (tested good) compressor. Added oil to the compressor and to the system with R314a cans that had an oil charge.

I bought some cans and attempted to charge it (Yes, I know this isn't the best way to do it, I've been doing it this way with my cars for years. Does it have optimal performance? Nope. Does it work and is it cheap? Yup.)

So I turn on AC full blast. I empty a can into the system, everything seems ok, clutch engages and compressor is turning. No cool air. I empty another one. Still no cool air. The gauge on the low side connection hose says pressure is low, not even on the scale. OK, usually 2 is enough but I begin to add another. The pressure relief valve opens. Really weird, considering pressure is still nonexistant on the low side, and no cool air from the vents.

No bubbles in the sight glass on the receiver. The hoses going thru the firewall to the evaporator aren't cold at all.

I have a factory service manual, and making the assumption that the high side is very high (as it would be if the relief valve is opening) and the low side is very low, it advises that either the expansion valve is bad or there is a blockage. How can I verify the functionality of the expansion valve (Is it possible to install backwards? I don't think so...port sizes seem different)? Any other advice on what steps I should take next?

Sorry about the book. Also, if you're going to launch off in a tirade about how I need to pull a vacuum before I fill it, save it. Should I have a shop evacuate my system? It seems silly to waste $30+ in freon and have to buy more. I assume they'd gouge me on it. I also feel like anything I do can't be properly tested until I try to fill the system again, which could lead to more freon wasted. Really don't want to be buying hundreds of dollars of freon...

Thanks in advance for any help you can provide.

Are there service valves on it? Are they open halfway?

There are service valves. They are not open halfway. Did that answer your question?

did you evacuate the air from it? it will never work right with air in the system, does the clutch cycle at all when you turn it on?

decathect said:

There are service valves. They are not open halfway. Did that answer your question?

Click to expand...

Ah, yes it did. They need to be open halfway.

Try the search. You'll find all you need about them and how to open/close them properly.

The service valves have 3 positions. 'open' and 'closed' aren't explicit. I should have specified.

the 3 positions:
1. Isolate compressor (screwed in all the way)
2. Activate ports (could be considered 'open halfway') - should only be in this position when you are charging the system.
3. Deactivate ports - system active (screwed out all the way)

When I am expecting the AC system to be working, i have them at #3.

Don't need to search. Have, and have read and re-read the factory service manual.

Jnida63 said:

did you evacuate the air from it? it will never work right with air in the system, does the clutch cycle at all when you turn it on?

Click to expand...

It will blow cold with some air in the system. I don't think you read my initial description thoroughly.

Pulling a vacuum is done for two reasons, one is the Air does not condense and thus causes hydraulic flow problems (not a complete killer issue) the second reason is to remove water vapor (humidity) as it will chemically react at elevated temperature and pressure with the refrigerant, forming corrosive acids, and then load up the drying agent in the desicant-filter, which can clog the desicant media....and restrict flow.

Sounds to me like some junk got in the expansion valve, or the expansion valve was bad out of the box. Also sounds like you may have WAY too much oil in it now, which can cause flow problems, but I am not sure that would cause the low pressure you have. Is the low side showing a vacuum, or do you not have a gauge that can show vacuum on the low side?

I had your problem twice in a row, one was a bad condenser fitting (custom) weld job that had sealed off the inside of the fitting, replaced that, and the next problem was junk from the old parts came loose and stuck in the new expansion valve. I had to flow test each part with compressed air, to find the bad fitting-weld job, as it was an assembled elbow....

I use gauges, and in my case the low side dropped to about 25" vacuum before I ever got close to overfilled it, or blowing the high pressure relief valve. Harbour Freight sells a low cost professional AC gauge set on sales for as low $35-$39 at times, well worth the money.

Thanks ecoMike. I do realize why it is done, but like I said, i've done it this way for years and my AC systems have functioned acceptably well. I'm sure it reduces the life of the dryer.

Anyway, I'm starting to think it has got to be the expansion valve as well. The spec for oil for the entire system is 4.5oz. As I figure i'm at about 4-5oz, should be about right.

I have been avoiding buying those HF gauges as people say they don't last very long before they break, but I suppose if I can get a use or two out of them, its worth it.

decathect said:

Thanks ecoMike. I do realize why it is done, but like I said, i've done it this way for years and my AC systems have functioned acceptably well. I'm sure it reduces the life of the dryer.

Anyway, I'm starting to think it has got to be the expansion valve as well. The spec for oil for the entire system is 4.5oz. As I figure i'm at about 4-5oz, should be about right.

I have been avoiding buying those HF gauges as people say they don't last very long before they break, but I suppose if I can get a use or two out of them, its worth it.

Click to expand...

I have had my HF set for a good 8-10 years now, no problems. Used them probably 30 times already. They are good quality.

Do you know of any cheap/easy way to re-use freon? That's whats killing me now.

Cheap? NO.

Easy, yes, a shop with a rig, LOL.

yeah, boo! I'm crazy enough that I've been looking on craigslist in the hopes that a used rig pops up cheap.

Alright, coming back to the brain trust for more help. I got the A/C manifold as suggested, and it was helpful. It confirmed that in fact, my low side I had basically zero pressure, and on my high side I saw it peak to nearly 400 psi before I shut it down. It kept creeping up to no end, which would explain why it kept blowing the relief valve.

I think the problem had something to do with this unique set of fittings and spring valves... not sure if that would be correct terminology. I'm almst certain that there is a problem with this setup, or by design it is supposed to greatly restrict the flow? I thought the only 'restriction' by design was the orifice going into the evaporator. Need help/explanation on this. The left end is the hose that goes to the expansion valve (high side) and the right end is what connects to the dryer/receiver.

What is this, what purpose does it serve, and how do I ensure it is functioning correctly? If this isn't the problem, it has to be the dryer/receiver.

Thanks for the help!

It was used to hold the R-12 charge during factory assembly, and it is obsolete, an unneeded artifact. It was a one way check valve. Most of us reused the outer fittings (No longer available), and we just leave the guts out.

There are two of them, one at the condenser and another at the filter / dryer.

huh, I didn't see one on the condensor. Although I did replace it. should it be on the upper or lower connection, and is it attached to the hose or the condensor itself? Thanks again, EcoMike!

I forget, my 85 had one on the top inlet to the condenser, and the 87 and 89 had one on the filter dryer. I forget if they just moved it, or if there were two on each. They were both on the small lines, the high pressure lines.

Well, it's not a check valve (allows flow in only one direction), it's a quick disconnect. There's only one. True, it's not needed.

The green o-rings show that it was taken apart before and the old black rings replaced. Looks like it was assembled wrong if the way you show it is the way it came apart.

Leave the 2 parts with the springs out and try again.

Picky, picky picky, LOL, so it is a quick disconnect valve, LOL:worship:

Certainly looks like it could have been a one way valve, but I have never seen them new, or the specs on the OEM part...etc. and I guess there was no valid reason for a one way valve, so I can't argue the point.
:cheers:

how should it have been assembled?