Poor cooling suddenly?

[Fussybob]

I hope someone can help me.

1988 Buick, Electra Park Avenue, 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.


Testing conditions………

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 speed raised to 2000 rpm for 5 minutes...….

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?

[Cornbinder89]

Is the compressor clutch cycling? If not you could have a bad (leaking) valve in the compressor or a slipping clutch. From you description I don't see where you messed with the charge amount, good! Hard to diagnose this type of problem over the net, It seams like the compressor can't draw the low side down low enough.
Normally if this was a problem that slowly came on, it would have more possible causes. Where it was working fine, then the next day is not, it is unlikely a refrigerant loss or low charge are to blame, esp if the clutch is not cycling, it is more likely to be the compressor itself.
I would have a shop look at it rather than take a gamble and throw expensive part at it.

[Fussybob]

Thanks for the reply!

The clutch is not cycling, it is always engaged (compressor pumping). With cold engine, first turn on of the AC no improvement of getting cold air out of the vents over a 5 minute period., vent air temp is about 65 to 70 degrees during that 5 minute period. I assume that the clutch would only cycle when the evap temp was low enough?

The clutch pulley bearing on the compressor is rough sounding so that is shot. I heard a few compressor clatters when running. Plus the drive belt squealed a few times with maybe the compressor locking up.

I ordered a new compressor, accumulator, orifice tube. Hopefully the old orifice tube doesn't show any metal particles. Trying to break the line fittings on a 32 year old system will probably just not work to flush the system. Does flushing the system from the evap at the accumulator, through the condenser to the detached compressor line, and from the orifice tube down to the compressor detached line sound logical?

[Cornbinder89]

At very least, you need to separate the liquid line at the orifice tube and inspect the screen on the tube. Failure to remove any debris in the system that can then circulate back to the compressor, can ruin the new compressor. Then you have to do the job all over again.
If I had any question, I would replace the condenser. Not only are they hard to clean, they are subject to damage from road debris and de-icer sprayed on the roads.
It is your eyes on the system, you have to make the call.

[Fussybob]

This is my 94 year old father's Buick. He drives it about once a week, never sees salt and very rarely any rain. The car looks new, the engine looks new. I had to add about 1 can of R134A a year in early spring after it sits during the winter. I realize that the car sitting for months during the winter does nothing to lube the compressor shaft seal. I try to run the car in the garage at least once a week in the winter. With the defroster on it will cycle the clutch on and off.

This is why I'm thinking of flushing the system after the lines a are broken at the accumulator, the orifice tube, and at the compressor. I should be able to do it good. If I see no debris at the orifice tube screens then maybe no flushing is required?

[Fussybob]

OK flushed the complete system, replaced the compressor, receiver/drier, orifice tube all o-rings, 8 oz of PAG150 oil.. Pulled the vacuum for an 2 hours, let sit for 1 hour and no leaks. Put in 30 ounces of R134A ( calculated from GM's R12 to R134A conversion information). Runs great! Today it is 90 degrees F ambient, vent temperature is 40 degrees F, this is at idle, sitting still in a garage.

Now I have a problem where I removed the receiver/drier low side port schrader valve core as I was putting on an R134A service valve adapter with its own core and said why do I need 2 cores in series. Well when I went to remove my low port service hose from the low port valve the freon along with some oil shot out, I immediately put the service hose back on and determined that the the low side port adapter doesn't have a core valve in it!!! I need to purchase a new adapter valve with a core and try to switch this very quickly. Any one have any suggestions on any way to do this switch without losing my freon/oil charge???

[Cornbinder89]

If it doesn't have a core, there is going to be no way to take your hose off and change the fitting or install a core. There are tools that let you swap out cores without a loss of charge, but you need to have that special tool on the fitting before removeing and replacing the core. ANy attmept to remove the hose will result in a total loss of charge.
You don't want to leave the core in the R 12 fitting either, Two cores in tandem will not work either.

[Fussybob]

The R12 to R134 port adapter (made the conversion in 2004) didn't have a core just a spring loaded pin that pushed against the core in the accumulator. I didn't know this and removed the core from the new accumulator believing that the old conversion port adapter that I reused had a core in it. Well this is what I did, I quickly removed the service hose, and quickly screwed the cap on the adapter (wasn't that hard to do system static pressure was 70 psi), removed the adapter and then quickly swapped to the new adapter with a core. I had some freon loss and minimal oil loss as I had a white sheet covering the engine, my oil has a dye in it so there was only one small area of dye on the sheet. My service hoses are 5 feet long I had them off and on a few times so I lost some freon there. I had 4 ounces of freon left in the can that I originally filled the system with, so I just added that amount. A/C works just fine. So yes you can swap ports and lose not loo much freon if you are fast enough!!!

[Cusser]

Nice to know, Fussy !!!

I had a 1984 Jeep Cherokee with manual on-off service valves, thought those were really useful. Wonder why that style went out of favor.

I once replaced its compressor with a used one, and didn't lose enough R-12 to matter !!!

[Fussybob]

OK i need guidance/confirmation on what I see today.

The ambient is 85 degree F, Humidity is 50%.

The A/C was set to 60 degree F, low blower, re-circulation is on.

Started the car, the A/C clutch cycled ON for 10 seconds, the OFF for 10 seconds. It this 10 to 15 times, then ON without any cycling.

After 10 minutes of running at idle only the Evaporator inlet pipe and the Accumulator body were both at 50 degrees F.

Vent temperature is at 40 degrees F.

I notice that I get a lot of Accumulator condensation, and after driving the car a large amount of water draining out from the Evap drain. I never noticed that before. I normally set the A/C to above 60 degrees F, usually 67. On this Buick the inside air auto re-circulation ends after 60+ degrees, and outside air only from 61+. There is no way to "manually" control re-circulation ON or OFF.

My question is with my 50 degrees for both the Evap inlet and the Accumulator, do I have enough Freon in the system?

[Cornbinder89]

Nice to know, Fussy !!!

I had a 1984 Jeep Cherokee with manual on-off service valves, thought those were really useful. Wonder why that style went out of favor.

I once replaced its compressor with a used one, and didn't lose enough R-12 to matter !!!

My 1992 Marmon semi tractor was the newest vehicle I've seen that still came with them from the factory. You can add them (still available from A/C supply houses) If you have room.
Room, and the fact you can damage a compressor if you leave the outlet closed, was why they went a way.

[Cornbinder89]

OK i need guidance/confirmation on what I see today.


Started the car, the A/C clutch cycled ON for 10 seconds, the OFF for 10 seconds. It this 10 to 15 times, then ON without any cycling.

After 10 minutes of running at idle only the Evaporator inlet pipe and the Accumulator body were both at 50 degrees F.



I notice that I get a lot of Accumulator condensation, and after driving the car a large amount of water draining out from the Evap drain.?

When you 1st start the system, the orifice tube is only metering vapor, so the suction side rapidly dips to cut-off pressure, once liquid reaches the orifice tube, and makes it through, the liquid expands to much more vapor than is allowed through the orifice tube when vapor is at the inlet.
The reason you see a lot of condensation on a day with 50% humidity is the evaporator and accumulator are cooled to below the dew point, and the water condenses.
Hard to judge amount by what temp, but I'd say if both the inlet of the evaporator and the outlet (to the accumulator) are about the same temp, that you are close. If the inlet of the evaporator is much colder than the outlet, then you are low.

[Fussybob]

Thanks for the info on the orifice tube only metering vapor on start up, makes sense. I'm learning a lot with this project.

Both my Evap inlet and outlet are at the same temperatures so I will just say that I have the correct amount of Freon at this point.

Thanks for your help and guidance!

[Cornbinder89]

Even on a Tx valve system the suction side will dip quite low before recovering to a more "normal" pressure on start-up. It does so for the same reason. Vapor at the metering device.