A/C repair failure - stumped

[swsl]

First time to attempt repair but pretty well informed. Here's the story:

AC failed while driving. Went from good to zero cooling in a matter of minutes while driving. No noises.

Clutch was engaging, low side and high side pressures were the same with compressor running as static readings. Right around air temp on both sides.

This indicates a bad compressor or internal pressure valve, right? So I replaced the compressor along with a new drier and expansion valve.

Old oil looked fairly clear, by the way.

Pulled, flushed and dried the hoses and condenser thoroughly. skipped flushing the evaporator to avoid trapping fluid in it. Just ran some filtered compressed air through it to verify good flow.

Filled comp with specified oil and hand turned it once installed.
Then I pulled a vacuum and let it sit, no apparent leaks.
Filled on both sides what little it would take with engine off then turned on to charge the low side but it would not take any more charge.

Clutch was not engaging, fans not coming on. So I jumped the trinary leads and clutch engages, fans go on. But manifold gauges continue to show same readings working as static, no compression appears to be happening, no freon getting sucked into system.

I think that perhaps I damaged the trinary while flushing and have ordered another.

BUT STILL, jumpering it and getting the clutch engaged on the new compressor to turn should allow me to keep filling, right?

All I can figure is that either the new compressor is bad or else there's something I'm doing wrong.

So- any thoughts? I am assuming that if I can jump the leads for the trinary and get the clutch operate then the upstream relays and controls should be good, right?



UPDATE: After getting another gauge set and changing out the Trinary to no avail and also testing the expansion valve, I traced the failure to show any compression to the brand new service valve on the Low side being stuck shut. Weird issue.
So the low-side gauge was only showing the charge that made it into the manifold hose and I couldn't tell that it hadn't entered the actual system. The Trinary was fine, it just was not seeing enough pressure on the low side. The expansion valve was fine.

Anybody experienced probably would have noticed that very little gas left the can and it didn't get cold as it should, but I did static charge through the high side also and that took in about 1/3 of the can.

Unscrewing the low side port and testing it by blowing through the port with the manifold fitting attached located the problem area and swapping out the new part for the older low side service port/valve solved it.

Lesson learned! No matter what, don't assume that new parts are all good! I had never imagined that the new shrader (ish) valve would be stuck closed. Leaking, sure, but it was simply not opening even when depressed. Had even tested it with four different adapters on it in case one of the valve depressors was failing. None would open it.
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2002 EV WK

[Stripped66]

What are the low-side and high-side pressures, and ambient temperature with the engine off?

What is your source of freon (30 lb tank, or the little canisters)? Are you purging the feed line into the manifold before running freon into the system? For how long did you attempt to charge the system (this is not a quick process with a 30 lb tank, and would be considerably slower with the smaller canisters)?
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[swsl]

[Abscate]

After adding PAG you have to manually spin the compressor about two dozen times to spread the oil out - if it locks it will damage the valves and then not compress. you also have to engage the compressor at idle only for the first 10 minutes or so, to give the oil time to spread out.

Static pressures mean nothing.

If you aren't getting any difference between the low and high with clutch engaged, either the compressor is damaged or the expansion valve is damaged.

The Sanden compressors are hardy, I doubt you killed it.

In NM, you want to be on the low side of the 950g spec, not high. Common mistake. More refrigerant does not mean better cooling.

This is a manual AC, single EVAP EuroBus , right?
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.ssS!

[swsl]

[Abscate]

I do have an old Sanden that works but is noisy. I think you got a bad one, also known as OBQ - out of box quality problem.

If you are detailed enough to do as you've outlined, I have 100% confidence in your fitment skills. Bad parts suck.

Let me know if you want to try my backup as a diagnostic - lot of work but that might be all you can do at this point.

[Stripped66]

[Abscate]

If you’ve vacuumed out the system the first charge will go in with a whoosh and the low side should start responding to the compressor. A can open to vacuum will empty about half its contents right away, enough to get some cooling.
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.ssS!

[swsl]

[swsl]

[swsl]

I just tried the test for the expansion valve that my friend suggested and it failed. But I'm not 100% convinced it's a good test.

I static charged the high side only, keeping the low side manifold valve closed. I was told that the expansion valve should be letting the vapor through from high to low and the charge should show up on the low side gauge as well, passing through the evap.

But it didn't. Low side gauge still shows vacuum while high side now has pressure. Again, Expansion valve is new, OEM from VW. All lines were flushed and the evap passed compressed air from one port to another when exp valve was off.

Is this a valid test?
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2002 EV WK

[Abscate]

I think you have nailed it, well done.

Bad Expansion valve. I think it takes the Audi valve

701820679D
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.ssS!

[Stripped66]

[swsl]

No luck. Swapped out the expansion valve. I had an aftermarket one that came with the compressor. All three (old, OEM and cheapo) seem to be passing air when I blow thru the high side. No sign of being stuck closed.

I also double checked that the evap is allowing air flow. Was starting to wonder if the new drier came clogged but it's not in the chain from high side service to low side.

I attempted to pressurize the system with compressed air and now started getting problems with leaks in the loaner manifold set.

Also started to suspect the service valve (the R134a not really shraders) that I replaced on the low side is not functioning right. After pressurizing the high side again (best I could with a manifold leak)with air and seeing no pressure again on low side, I pulled the service valve on the low side and yes, some air did hiss out. So maybe it's been blocked on the low side all along? Was I just seeing the static hose pressure on the low side instead of the actual system?

My head is spinning. And we hit the road tomorrow, heading for TX.

I think my best plan from here is to order a Yellow Jacket manifold and tackle it again when in Houston at mom's.

Thanks for all your help, will be back on it in a week or two.

Steve
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2002 EV WK

[swsl]

[Abscate]

My manifold set is one of the few Harbor freight tools I own and has done about 2 dozen jobs for me at this point. I did add a real vacuum gauge to it with a shutoff for system vacuum testing though
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.ssS!

[Stripped66]

Sorry to hear, but glad you didn't invest any further time or money into returning/replacing components at this point.

At the very least, draw a vacuum on the system and leave it under vacuum until you return. NM is certainly more arid than the dirty south, but the compressor oil is very hygroscopic and becomes acidic as it absorbs moisture; likewise, the desiccant in the receiver/drier will eventually saturate if you leave the system open.

Let us know the prognosis with the new manifold/gauges when you return!
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[swsl]

OK, I'm back on it in TX

The low side service valve was bad and not opening. The new replacement. What a pain that caused. The loaner manifold and adapters were probably fine. The old service valve was fine, I had just replaced 'em both because the high side was leaking a bit.

So, before I attempt to charge again, I have a new concern: Back in New Mexico, I returned the loaner vacuum pump but then managed to accidentally crack open the system afterward. So I lost vaccum and air sat in the system for two weeks. I went ahead and replaced the drier (again) before pulling a good long vacuum today.

Should I really be worried about the compressor oil in the system? I would rather not pull it. And the oil is now probably somewhat distributed, I imagine. Is it reasonable to expect that the fresh drier installed for those two weeks did it's job with a system full of air and then pulling a vacuum? And/or that pulling a vacuum helps clear moisture out of the oil?

The oil came in the compressor and I don't know if it's Double end capped. or whatever the newest preferred version is called.
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2002 EV WK

[Stripped66]

I believe the major concern is that when the compressor oil absorbs water it becomes acidic. However, I don't know how much of a factor this might be in the lower-humidity southwest as it would be where I am in the southeast.

Given that you did not exactly have the opportunity to run the system long enough to distribute the oil you initially added (I'd argue that most of it was probably in the receiver/drier), I would drain the oil from the compressor and put a vacuum on the system for several hours (or more) to evaporate any residual moisture (edit: seems you've already done this...). Somebody might make the argument for flushing the system, and perhaps a commercial A/C service flush/fill station could effectively neutralize any residual oil that was contaminated; but, unless you can circulate solvent through an evaporator or condensor yourself for an extended period of time, you're not going to flush out the old, residual oil. YMMV.

Fill with new oil, but don't put the entire volume in the compressor; follow the guidelines in the Bentley manual. It's something like 50% in the compressor, 15% in the receiver/drier (you could either add this to the high-pressure line leaving the compressor, or just put a bit over half of the oil in the compressor since most of it will go to the receiver/drier anyway), 15% in the condensor, 10% in the evaporator, 10% in the low-pressure line returning to the compressor. I don't have the Bentley manual in front of me, so these percentages are approximations from memory. (sorry!)
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[swsl]