Very weak cooling suddenly?

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Fussybob
Posts: 4
Joined: Sun Jul 26, 2020 1:01 pm

Very weak cooling suddenly?

Postby Fussybob » Sun Jul 26, 2020 1:24 pm

I hope someone can help me.

1988 Buick clutch/orifice tube system. Converted to R134A 15 years ago.

Cooling was great yesterday at startup when driving for 5 miles and the suddenly very poor/no cooling.
Under normal working AC system interior center vent would give 38 - 42 degrees F output air

Checked today.....
Ambient 88 degrees F, 42% humidity

Static pressure: Low side - 98 PSI, High side 98 psi.

Idling at 600 rpm, AC clutch engaged.

After 10 minutes of operation, windows open, blower on high, AC temp set to 60 degrees F, radiator cooling fans on

Accumulator temperature - 68 degrees F
Evaporator temperature - 69 degrees F
Interior center vent temperature - 68 degrees F

Low side pressure - 60 psi
High side pressure - 160 psi


Test data with engine at 2000 rpm...….

Accumulator temperature - 59 degrees F
Evaporator temperature - 64 degrees F
Interior center vent temperature - 60 degrees F

Low side pressure - 40 psi
High Side pressure - 275 psi

Any suggestions on what may be wrong?
Al9
Posts: 153
Joined: Tue Mar 10, 2020 3:26 am

Re: Very weak cooling suddenly?

Postby Al9 » Sun Jul 26, 2020 2:58 pm

Knowing which Buick from 1988 it is is important, since at least 4 Buicks from this year come with a GM V5 variable displacement compressor.
These ones have a control valve which can fail (they used to come without filters, new replacement ones come with them instead, maybe it's just a matter of debris eventually making its way in the wrong place) and leave the compressor unable to keep the proper piston stroke. Basically the compressor will seem dead at idle since it's running fully destroked. Replacement of one is easy and cheap. Also, proper operation of the variable displacement mechanism as a whole relies both upon correct refrigerant charge weight (fix any leaks and charge by weight) and correct piston/cylinder wall clearance (unfortunately the only viable fix to this condition is compressor R&R).

Sudden onset makes me think of a V5 control valve failure.
Fussybob
Posts: 4
Joined: Sun Jul 26, 2020 1:01 pm

Re: Very weak cooling suddenly?

Postby Fussybob » Sun Jul 26, 2020 7:13 pm

It's a 1988 Buick Park Avenue Electra with 3.6L engine. According to the service manual and what I can see visually, the system uses an Orifice Tube.

HR6, DA6 Compressor w/ Clutch

From all my data does this look like a bad compressor, and nothing else?

The clutch bearing is making noise so I'm going to just replace the entire compressor. I just don't want to find out that some other component or blockage is my main non cooling issue.

To repeat the system was cooling just fine for the first 5 miles yesterday and then just suddenly stopped cooling.

I'm leaning towards a bod compressor, I'm not any expert in AC, so just looking for guidance and thought all the data that I supplied could possibly alert someone that had the similar problems. Isn't my low side pressure kind of high at idle?
Al9
Posts: 153
Joined: Tue Mar 10, 2020 3:26 am

Re: Very weak cooling suddenly?

Postby Al9 » Mon Jul 27, 2020 2:22 am

Many things can go wrong with such an old car. This is really weird, especially the warm out of the blue part, but definitely sounds like the compressor has lived its long life and is now lying on the death bed (knocked too many reed valves off perhaps? no sump unlike with the A6, with double acting pistons, and PAG 150 if it has been switched to PAG oil during the conversion, doesn't seem like a long lasting design either). Only real way to be sure you don't have blockages is to thoroughly flush, and replace anything that can't be flushed (such as the orifice tube). Keep in mind that hoses meant for R-134A come with an internal layer that can delaminate from the actual hose material over time.
Fussybob
Posts: 4
Joined: Sun Jul 26, 2020 1:01 pm

Re: Very weak cooling suddenly?

Postby Fussybob » Sun Aug 09, 2020 9:07 am

Just as a follow up....

I replaced the compressor, accumulator, orifice tube, flushed the system, added 8 oz of PAG150 oil, pulled vacuum with no leaks, added 30 oz of 134A Freon.

Everything is fine, 40 degrees F out of the vents on an 86 degree, 52% humidity day.
Al9
Posts: 153
Joined: Tue Mar 10, 2020 3:26 am

Re: Very weak cooling suddenly?

Postby Al9 » Sun Aug 09, 2020 9:37 am

Good, so you replaced a dying comp in time before it had a chance to seize up and do more damage. Enjoy your cold air.
Fussybob
Posts: 4
Joined: Sun Jul 26, 2020 1:01 pm

Re: Very weak cooling suddenly?

Postby Fussybob » Sun Aug 09, 2020 2:07 pm

Al9 wrote:Good, so you replaced a dying comp in time before it had a chance to seize up and do more damage. Enjoy your cold air.


Yes, I found no metal on the orifice valve, but it was clogged with other muck.

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