Automotive Air Conditioning Information Forum

Hello,
New to the forum. Seeking AC wisdom...getting headaches from this situation below. Sorry in advance for this long ignorant post...

98 Buick Park Ave 3.8L NA
-AC system worked for previous owner, circa 1 year ago, but he would only have cold air for 2 weeks after adding freon. Diagnosed at shop as leaking somewhere near compressor, wasn't sure where precisely. No components were changed.

My efforts, chronologically:
-Flush of discharge lines, except line w baffle
-Flush of suction lines
-Service kit (orifice tube, accumulator, seals, oil on each component)
-Reseal kit into original Delphi compressor + shaft seal. Before installing, refilled w 9 Oz of pag 150 per directions. Clutch face down for several minutes prior to install, for shaft seal...turned by hand several revs.
-24 hr vacuum on system (was concerned of excessive water in system). Went through several rental and store bought vac pumps after getting less than expected vac readings...
-2.5 hr leak test/vac hold, no needle change.
-Recharge attempt: system will not build pressure on high side. Lo side gauge builds with introduction of freon and compressor would clutch in with several ounces of 134a but would not build higher than what lo side reads. Clutch off, hi side builds slightly and lo side dips slightly. Ended with lo side around 50, hi side same.

Round 2.
-Believed orifice tube may not have been seated fully, checked this and tube was loose, not in all the way or so it seemed. Seated it and reconnected.
-Vac test 2 hrs, leak test half hour or so...repeat of symptoms.

Round 3.
-Guessed weak compressor, installed a junkyard comp as an experiment...I know, prob not bright idea...same thing.

Round 4.
-New compressor. No change. Out of ideas!
Only difference here is that new compressor did not clutch in automatically. Jumped several times but no pressure build.

I'm thinking some of the above actions were unnecessary or just plain ignorant. I am clueless at this point.
Just some notes, air was bled out of cans prior to introduction via the Schrader valve.
Started w car off, then turned on after several minutes.
Lo side fully open, hi side open only to gauge.

Blockage in lines? Wouldn't that be a high hi side and low lo side??
Wrong orifice tube? Instructions in kit said to match color of original tube, which I did.
Passed leak tests fine...made sure amount of comp oil was correct amount and type.
Each compressor spits air when turned by hand, can hear and feel air movement, but I don't know enough to tell whether that is a sufficient metric for functionality? What is a good way to tell?
I keep thinking that something is either not producing pressure or is not restricting it. But shouldn't a new comp rule out the former, and a new, seated o tube the latter?
Utterly clueless and angry beyond articulation. Literal headache.
Please toss the life preserver, someone, and educate this poor hapless fool...

Thank you all

A few things come to mind.

That high side handwheel on the Manifold Gauge Set (MGS) should be closed at ALL times (this is an important safety issue) except when evacuating a system or charging liquid into the high side with the engine off. You will still get a gauge reading on the high side with the MGS handwheel closed.

Air should be bled from the yellow hose at the MGS, not at the cans.

How much refrigerant did you charge into the system by weight? It sounds like it's low, based on the static pressure readings.

What was the ambient temperature in front of the grille when you were charging it?

John,
Thank you for your response.
I had the handwheel closed to hi side during charging, only was open for vacuum and leak tests. I would like to know more about liquid charging to the hi side. I have heard this can be a bad thing?
Yes, air was bled from the schrader on the MGS, not the can directly. Bled until liq/gas spray exited.
No more than a half can (6-8 oz?) seemed to make it into the system each attempt; this was engine running, clutched in, rotating can 12 to 3 o clock etc, just would not build pressure over several minutes, which made me think something was wrong, so I would halt the recharge attempt. My understanding is that hi side should build fairly rapidly in a fairly short amount of time, while adding the freon? Not seeing this, I would quit trying within a few minutes, for fear of harming something... perhaps I am aborting too soon?
Ambient temp would have been around 75F.
I'm grateful for your attention.
Thanks

DSK777 wrote: ↑Thu Apr 25, 2024 9:44 am I had the handwheel closed to hi side during charging, only was open for vacuum and leak tests. I would like to know more about liquid charging to the hi side. I have heard this can be a bad thing?

Great that you had the high-side handwheel closed during charging. As for leak testing, one point that's good to keep in mind is a system that can hold a vacuum without leaking might leak under pressure (and vice versa).

As for charging a system, I prefer to charge refrigerant gas into the low-side service port only. Partial-charging liquid refrigerant into the high side can be done. However, I don't recommend it for safety reasons, especially for somewhat inexperienced home mechanics who might make a mistake and get into serious trouble. I strongly recommend charging gas only into the low-side service port (refrigerant container upright) with the high-side MGS handwheel closed.

DSK777 wrote: ↑Thu Apr 25, 2024 9:44 am Yes, air was bled from the schrader on the MGS, not the can directly. Bled until liq/gas spray exited.

That's the way to do it.

DSK777 wrote: ↑Thu Apr 25, 2024 9:44 am No more than a half can (6-8 oz?) seemed to make it into the system each attempt; this was engine running, clutched in, rotating can 12 to 3 o clock etc, just would not build pressure over several minutes, which made me think something was wrong, so I would halt the recharge attempt. My understanding is that hi side should build fairly rapidly in a fairly short amount of time, while adding the freon? Not seeing this, I would quit trying within a few minutes, for fear of harming something... perhaps I am aborting too soon?

Engine (and compressor) should be running at about 1,800 RPM while charging and testing. If the engine is at idle, the compressor isn't doing much of anything, so charging will be more difficult.

Are you sure you have your charging adapters securely attached to the service ports and the thumbwheels on the adapters turned to the fully open position (clockwise, not counter-clockwise)?

I don't recommend rotating the can. I would worry about injecting some liquid refrigerant into the low side and "slugging" the compressor. A liquid can't be compressed, so if you introduce some liquid refrigerant into the compressor instead of only refrigerant gas, something internal is almost sure to break, which would require another compressor replacement, along with the condenser.

Speaking of the condenser, it's also possible that you have a blockage inside of it. Moreover, professional MVAC shops always replace the condenser whenever installing a new compressor, which the compressor manufacturer requires (along with accumulator replacement) for warranty purposes.

DSK777 wrote: ↑Thu Apr 25, 2024 9:44 am Ambient temp would have been around 75F.

Not bad, but it's best to wait until the ambient rises to 80°F or above for MVAC work. You could try placing the cans in a bucket of warm water to warm the cans and speed-up the charging process. Also, the warmer the ambient temperature, the easier and faster the refrigerant will flow into the system.

As for the cans themselves, rarely does each one contain a full 12 ounces (net weight). That's why it's always best to use a refrigerant scale to ensure that you've charged precisely the correct amount, which is very important.

The specs that I have for your car are as follows: 32 ounces net weight of R-134a, and 9.0 fluid ounces of PAG-150. If you find an underhood decal that differs, the decal always takes precedence.

Lastly, you mentioned that you put all nine ounces of PAG oil in the compressor, which was probably too much if you didn't replace the condenser and flush the evaporator. A better way to add the PAG, I think, is to oil-balance a completely dry system. By that I mean to put a few ounces in each component, and then the rest into the compressor. The way to do that is to put about 1-1/2 ounces each in the condenser and evaporator, 3 ounces in the accumulator, and then 3 ounces in the compressor. Doing it this way will ensure that the compressor receives sufficient lubrication on first start-up.

John,

Thank you for all this information. I'll change many things for the next attempt...

I am sure that the adapters were connected and turned CW. I wondered about a leak, but thought certainly that a satisfactory vac test ruled it out. Your statement on that intrigues me.
I thought of the condenser. This is a charity case for an elderly family friend, so we are trying to keep it low budget. I realize there is risk in this...I was more willing to give it a try mainly because the former owner had working AC last known, and there was never any catastrophic failure that we knew of.
I tried a junk walmart digital scale to weigh the cans. I'll need to change to a better scale.
Thanks for the specs info and the advice re the oil.

I want to pick your brain a bit on some general questions.

-Because I have had 3 different compressors all demonstrating the same results, are there ways to tell (in general) whether a compressor is in condition to work adequately? On the original compressor, I could lay it on the bench and turn the clutch with one finger. The new one took a palm or the whole hand to turn. All of them pushed some measure of air out when turned, holding in hand.

-Given normal conditions, at an ambient temp of 80F, can you give me an idea how long it may take to recharge the 32 oz system I have? I realize other factors influence this. Perhaps there is an amount of time I could use as a general benchmark.

-I may be extra stupid: re the can tap, I am seeing people pierce the can with the tap, turning CW, then back off the wheel on the tap CCW until it stops. My understanding is that most of these cans self seal like a schrader valve, and thus the tap must be fully CW to let the freon out. Am I backwards? My ignorance is bounded only by the length of the day, sometimes. They do state they are self sealing, but I thought I might verify.

-This car has auto temp control. I have it set as cold as possible (60F), with blower running, moving air, in recirc. Anything particular to know about an auto temp system during recharge?

Thanks so much for your helpful advice. I registered in this forum for education and you are helping me immensely.

A note that came to mind:

I am seeing oil around the compressor seals. I remember putting several drops on them prior to my installs, but the amount I am seeing looks like there is too much there than what may have come off of them as I tightened the suction/disch lines down. That said, I have reused these seals at least 3 times with my compressor swaps. Line is being tightened firmly w open end wrench, as I cannot get a torque wrench into this spot. 13 ftlbs I am thinking.

I feel stupid to ask...are compressor seals reusable for a couple times? Doubting it is best practice, but perhaps enough to cause failure?

Maybe this is my problem. They were new seals from the AC service kit. But seeing the symptoms did not change from the first attempt thru the 3rd, maybe not a concern.
I don't mean to be tiresome, just musing...

Before we discuss further, let me ask these questions: After you installed the new Delphi compressor, did you attain a full system charge of 32 ounces, or only a partial charge? The reason I ask is that according to the Field Service Manual, your car has a variable-displacement compressor with a mechanical control valve. This type of compressor might not build the pressures expected on the high side with a full charge, much less a partial charge. Did you measure any pressure at all on the high side with the compressor engaged, engine speed ~1,800 RPM?

John,

Yes, hi side gained around 50 psi, max 60 or so, never exceeding the highest readings of the lo side.
Cabin air never seemed to change temp throughout.
I should note, the new compressor is a Denso 4719185; the first 2 attempts were Delphi's. The sticker was worn off the original Delphi so unsure of part #. Not much hi side psi difference, if any, amongst the compressors it seemed. The Delphi's clutched in almost immediately during charging, whereas the Denso has yet to clutch in on it's own, running around 50 psi hi side. I think it easily got the same amount of 134a if not more than the Delphi's.These numbers are the best I can remember...should have got photos.

Now, I have not reattempted yet. So all the previous attempts were at engine idle. I still have to recharge anew, following your recommendations.

I never attained a full charge, not even half, because after observing the hi side remain at lo side pressure, I would stop the recharge process thinking I was potentially causing system harm by not seeing things working correctly.

I will reattempt (on a warmer day) with your good advice, and advise of the happenings thereof.

I was re-reading my first post. I should have said, that when clutch was ON, hi side built slightly and lo side dropped slightly...probably around a 10 psi change. So it responded to clutching in, but didn't amount to much.

I sure appreciate your assistance.

Are you not swapping out the control valve in these compressors correct? Do they come with a new one installed?

DSK777 wrote: ↑Sat Apr 27, 2024 4:27 am Yes, hi side gained around 50 psi, max 60 or so, never exceeding the highest readings of the lo side.
Cabin air never seemed to change temp throughout.

Okay...you need to get the full, exact 32 ounces (net weight, not fluid ounces) of R-134a into the system before we can evaluate cooling performance.

As I mentioned, this car has a variable-displacement compressor with a manual control valve (pressure control) that, with a fully charged system, the compressor "attempts" to keep the low-side pressure at around 30 PSI for optimal cooling without icing-up the evaporator. How the compressor does that is a bit too much to explain in this post. However, the high-side pressure could be lower than expected depending on what point in the compressor's displacement cycle it happens to be.

For example, on an 80°F day after charging the system fully, I wouldn't be surprised to see a HS pressure around 110 PSI (minimal compressor displacement) with effective condensing, whereas, with a non-variable-displacement compressor, the high side would typically be around 200 PSI presuming the same ambient temperature and equally good condensing. A system having a non-variable-displacement compressor controls evaporator icing by other means. While you're charging this system, don't be deterred by the unusual high-side pressures.

DSK777 wrote: ↑Sat Apr 27, 2024 4:27 am Not much hi side psi difference, if any, amongst the compressors it seemed. The Delphi's clutched in almost immediately during charging, whereas the Denso has yet to clutch in on it's own, running around 50 psi hi side. I think it easily got the same amount of 134a if not more than the Delphi's.

Denso is a good, solid compressor brand. It's clutch didn't engage probably because there wasn't enough refrigerant in the system yet.

DSK777 wrote: ↑Sat Apr 27, 2024 4:27 am I never attained a full charge, not even half, because after observing the hi side remain at lo side pressure, I would stop the recharge process thinking I was potentially causing system harm by not seeing things working correctly.

Don't be deterred by the low high-side pressures, as I mentioned. They're undoubtedly due to the variable-displacement compressor. You won't hurt anything by charging the system to the car manufacturer's specs.

Since we're on a budget with this repair, we might take a chance and re-use the original condenser, although Denso won't like that for warranty purposes.

Over and above the warranty issue, how did the original OT look when you pulled it out, full of black gunk and plastic/metallic particles, or was it relatively clean? I'm wondering whether the original compressor had begun to disintegrate internally, sending its debris downstream into the condenser and beyond. In that case, the condenser would have to be replaced, especially a parallel-flow condenser that can't be flushed.