AC has me stumped - JeepForum.com
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post #1 of 16 Old 04-16-2021, 08:59 PM Thread Starter
Magnum
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Wj AC has me stumped

I have a 2004 Overland. Last spring, the AC was not cooling well. I added dye and found very small leaks at a couple of the fittings. I went through and replaced all of the O-rings, vacuumed and charged the system, and was good for the summer.
This spring, it was not cooling at all. I figured at 18 years old, it was time to replace the whole system. I bought a kit from Rock Auto that included the compressor, condenser, dryer, and expansion valve. I flushed the evaporator, replaced all the parts listed, and vacuumed the system. By the way, I followed the directions to drain the shipping oil and add 3 ounces of PAG46. The system held vacuum well. I charged with a partial can that I had (in addition to the 1/3 of a can put in last weekend), and the static pressure came up to ~70 PSI. Cranked the engine, and both the high and low sides showed 70 PSI. That was last weekend, and I ran out of time to do any more.
I thought that maybe there was not enough R134 in the system to liquefy yet. So today I hooked the gauges back up today, and it showed ~65 PSI. Today was at least 10 degrees cooler than last week, so I think that explained the pressure difference from last week to now. I connected a new can of R134 and put it in a warm water bath. The system took about half of the can quickly, and static pressures read ~85 PSI. I closed off the high side on the gauges and cranked the engine. Both pressures stayed about the same. The compressor clutch pulled in and stayed in, but the pressures never changed. I scratched my head a while and decided the high pressure hose must be blocked, since that was the only thing (except for evaporator) that I had not replaced. I got the refrigerant recovered, and pulled the high pressure hose. That hose is clear. I turned the compressor by hand, with a finger blocking the discharge port, and it is clearly creating pressure.
I am at a loss. Why am I not building any pressure on the high side? Or at least not showing any pressure on the gauges. It is a brand new compressor, and definitely pushes out when turned by hand, as described above. I guess it is possible that the new condenser is blocked, but how likely is that? Could my gauges be bad? Any ideas are welcome, because I am out of them.
Thanks


94 YJ, 4.0, 5-Spd, 33x12.5 GY Duratrac, RE 2.5" Lift
Brown Dog Mounts, 8.8 w/ disks, TrueTrac f & r
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post #2 of 16 Old 04-16-2021, 09:36 PM
WJ60
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Being an HVAC tech for 41 years now, 2 things come to mind.

1- Your gauges high side and low side shut off valves are not shut off, thus there is no pressure difference being seen.
2- The clutch, while appearing to be pulled in, is not engaging the compressor.


Even if you had something plugging a line or coil you would still see some pressure differential.
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post #3 of 16 Old 04-17-2021, 01:08 AM
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i agree could the gauge high and low valve be leaking? or open


Thinking out loud...
This is a TXV valve IIRC, what is result of it being stuck open?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #4 of 16 Old 04-17-2021, 03:21 AM
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If the TXV were stuck open there would still be a noticeable amount of pressure differential, assuming the interior components of the valve aren't missing.



To the OP: When you were manually turning the compressor and feeling pressure at the discharge connection, did you also feel the inlet to see if you were getting a suction? Is it possible you got the hoses connected backwards?
Even without gauges hooked up you should be able to feel a noticeable temperature difference between suction and discharge lines.
How many ounces did you put in compared to the amount listed on the sticker? Did you put it in as a liquid or as a vapor, ie, can up or down?

I'm just throwing out ideas here.
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post #5 of 16 Old 04-17-2021, 06:38 AM
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WJ60 with 41 years AC - I will be reading ALL your postings.

I am still thinkng gauge set was OPEN...
WJ60 and snowbuggy like this.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #6 of 16 Old 04-17-2021, 08:20 AM Thread Starter
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Thank you for all of the replies so far. I will get back on this project in a couple of hours.
The gauge valves seem to be working correctly, but I will double-check.
As for the clutch not actually turning the compressor: the inner "hub" clearly pulls in and spins. Is there some way that it could still not be turning the compressor? I will take a look at the old compressor to understand the mechanism.
Again, thanks for the input.
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post #7 of 16 Old 04-17-2021, 06:29 PM Thread Starter
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I still don't understand it, but it has to be the compressor. I checked everything for about the fifth time, put it all back together, vacuumed it down for about an hour, and verified that it held vacuum. Connected a can of R134 and charged through the low side port as vapor. Put the can in warm water, and got probably 10 ounces into the system. Static pressure was right at 100 PSI.
I pulled out the compressor relay, so I could energize the clutch with my Power Probe. I started the engine, and energized the clutch. It visibly pulled in and spun, but the gauges never moved. I mean they did not flinch. As I alternately energized and released the clutch, I noticed that the engine did not bog. So it seems that the compressor internals are not turning - not making any pressure and not loading the engine at all.
I am tempted to tear into it to see what is going on, but I guess that would void the warranty. After looking at the old compressor, the only thing that makes sense to me is that the compressor was built with the wrong clutch, and the hub is bigger than the splined shaft. I don't see another way that the clutch could pull in but not turn the compressor internals.
Any thoughts?
Thanks --

94 YJ, 4.0, 5-Spd, 33x12.5 GY Duratrac, RE 2.5" Lift
Brown Dog Mounts, 8.8 w/ disks, TrueTrac f & r
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post #8 of 16 Old 04-17-2021, 08:17 PM
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I suspected that might be the problem but it's hard to go down that road (being a new compressor) without seeing it in person. If you turn it with the hoses unhooked and feel suction and discharge pressure at the openings then it's most likely an external issue (clutch and/or associated parts). If no suction then it's an internal issue with the compressor. Keep us in the loop.
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post #9 of 16 Old 04-18-2021, 08:01 AM
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A small bit of advice:
Empty systems should always be charged with liquid into the high side.
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post #10 of 16 Old 04-18-2021, 01:50 PM
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How much refrigerant do you have in it? 1 and 1/3 cans? My 01 holds 24oz. 2 cans. There's a label on the right corner of the hood with recommended charge.

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post #11 of 16 Old 04-18-2021, 05:41 PM
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It can be difficult to get 2 full cans in a system when the compressor isn't running though.
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post #12 of 16 Old 05-02-2021, 12:07 PM Thread Starter
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I am back home after a two week trip, and still no joy. I had a warranty replacement compressor shipped in while I was gone. This one - unlike the first - said it had 3 oz of the correct PAG oil, and to add oil to bring it to spec. The chart said 4.5 ounces, so I added 1.5 ounces. I leaned it forward to coat the front seal as directed, spun the compressor several times, left it in that position for about a half hour.
I installed the new compressor, vacuumed the system down, and got 12 ounces of R134 into the system by putting the can in warm water. The hi and lo pressures both showed ~80 psi. Cranked it up, turned on the AC, the clutch engaged, and the gauges did not change at all.
WJ60, I just saw your note that a completely empty system should be filled with liquid on the high side. I did not do that - I added gas to both sides. I can see how adding as a liquid would be faster and get the system to pressurize more quickly, but would it keep the compressor from working at all? The only things I can think of are that my gauges are bad, or that the connectors do not engage the schrader valves correctly. I am going to get a rental set of gauges and see if they give different results.
Any other ideas?
I am admittedly just an amateur, but I have repaired a half dozen systems successfully, plus added AC to my YJ Wrangler. None of them gave me 1/10 of the problem that this one has.

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post #13 of 16 Old 05-02-2021, 01:35 PM
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Gauges are usually necessary for troubleshooting, charging, evacuating, etc. But if the compressor is pumping, and the charge is fairly close, then you should be able to feel the suction line get cold and the discharge line get hot.

If your gauges are at 0 psi when unattached, and go up to 80 psi when hooked up, then it's not the gauges. Equal pressures when a compressor is running can be caused by the gauge knobs being open, the compressor being bad, there is no metering device in the system, or your gauges are not depressing the schraeder cores as you said.


Typically when charging a system, liquid is charged into the high side only. You will see the low side gauge raise (proving schraeders are depressed) as the charge goes in. Once all the liquid is in, then the high side gauge is closed off, the system is started up, and the remaining charge is put into the low side.
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post #14 of 16 Old 05-02-2021, 01:55 PM
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You need to locate the sticker in the engine compartment that gives you the required amount of refrigerant. According to everything I've looked at you should be somewhere in the 24-27 oz range. Obviously 12 oz is only half the charge.
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post #15 of 16 Old 05-02-2021, 02:04 PM Thread Starter
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Success! But I'm not sure how.
I got a set of rental gauges, and they showed the same static pressures as my set, about 85 PSI plus or minus 5. I started the WJ, turned on the AC, and saw no change. I shut it off and decided to try to get some more R134 in the HIGH side.
Warning: do not try adding on the high side of a running engine or pressurized AC system with a regular gauge set. The pressure can be 250 PSI or higher, and the refrigerant can could rupture or a seal blow out.
But I could see that my high side pressure was 85, so I opened the valve to the high side and put the R134 can in warm water. I got the high side up to 125, and shut off the high side valve. I started the engine and turned on the AC. For a few seconds no pressures changed, then the compressor audibly changed, bogged down the engine, and High side pressure went up and Low side went down. WTH? At this point, I had probably 20 ounces of R134 in the system. I opened the low side and added a little more until the pressures matched the chart for 85 degrees. By weight, I put in a total of 26.6 ounces. Pretty close to the spec of 27. So everything seems great now. But what happened?
A couple of weeks ago, I tore down the old compressor to the point where I saw that there are 5 pistons that push into the front plate, which appears to route the gas so that each piston keeps increasing the pressure until it reaches the 5th piston, which has the compression output. Are those pistons driven both forward and back? Or are they driven in one direction and then either spring or pressure return? I am suspecting that they are pressure return, and they were floating at one end until there was enough pressure on the high side to push them back. Or maybe I don't understand at all and this was just some sort of voodoo.
Thanks for all the suggestions along the way. WJ60, I think your comment about adding to the high side was the key.
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