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Old 06-06-2018, 05:14 PM   #1  
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Default AC blows cool instead of cold

Need some opinions from you guys with AC experience please.
Car is a 1994 Le Sabre with approx 100k. Owned the car since it was new, AC system has never been opened up for any repair. Standard AC controls, no C68.

Noticed a few days ago AC was not cooling properly, air from vents was just cool. Outside temps were were approx. 80*. This car has always cooled down very well in a short time, even to the point of being cold even in the hot summer time in Ga.

These are some numbers I got today with manifold gauges.

Static at 80*
low side-82psi
High side-81psi

Started car up and for the first 3-4 minutes-low side-95psi
high side-100psi

Let car run for 10-15 minutes and got this-low side-115psi
high side-125psi


Compressor did not cycle during this time.
From what I've been able to find this is probably a worn out compressor? No noise from the compressor.

Any thoughts on those numbers?


Thanks
Joel
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Old 06-10-2018, 12:39 AM   #2  
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I would try adding half a can of R-12 and see if it doesn't blow cold again. The most likely thing is a slow leak. The high side pressure with AC running should be about 150 to 175% of the ambient temperature.
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Old 06-10-2018, 01:09 AM   #3  
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Do NOT add ANY R-12 to the system.

You can try adding R-134a, but I agree that it looks like either a failed compressor or possibly something on the expansion side.

If it'* the compressor, make sure the system is flushed out good.
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Old 06-10-2018, 09:41 AM   #4  
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I agree with Rjolly......

If the problem was low pressure, that low side would suck down to below 30 psi, and the controls would cycle off the compressor....

I can't remember if this has a thermal expansion valve or not......either the valve is wide open, or the compressor is not compressing if the clutch is engaging.....

the only reason why the pressures are going up on both sides is because of heat from the engine compartment....
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Old 06-10-2018, 09:51 AM   #5  
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Also, I don't think a '94 uses R-12.....it uses R-134a.......you will know by the service valves



Also, I don't think this does have a thermal expansion valve, only an orifice tube, so it looks like a bad compressor....

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Old 06-10-2018, 11:34 AM   #6  
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System is 134A

I did this test again with the engine cold/warm, first test was on a warm/hot engine.
This time the compressor did cycle and low side went to 45 and comp would cut off, drop down to 22 and comp would cut on. High side was 160, down to 125.

After several minutes engine got warmer, and low side started climbing again similar to first test. This is what'* strange to me. I've worked on a lot of AC systems over my years, never had this situation that I KNEW of.

I could mist the condensor with water and low side pressure would drop and comp would start to cyclye again?

I'm going to add a few ounces of freon later today. I don't like the idea of this but at this point there is nothing to lose. If it helps and system operate properly-good- if not then I'll replace comp, condensor, etc.

Thank for the replies,
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Old 06-10-2018, 01:25 PM   #7  
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Well, what you just posted is not what you posted in #1......
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Old 06-10-2018, 07:23 PM   #8  
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You are exactly correct on the difference in the numbers. This is what'* confusing me.

But both set of numbers in both posts is what the car was doing. I tried to be as exact as possible by writing down the pressures instead of trying to remember everything.

Biggest difference in first set versus second set is the temp of the car, as first set reflect a much hotter engine.
The other difference is during the second test I did mist water over the condensor when the low side pressure started climbing too high.

Sorry to be so confusing on this, just trying to give as much info as possible.

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Old 06-10-2018, 07:46 PM   #9  
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This is getting confusing, and this information may help to confuse it more, but hey, it'* worth a shot...


One thing that I have experienced was a condenser that wasn't able to dissipate enough heat, and it caused both pressures to run high. I believe this was caused by a drive through a bug swarm, followed by years of New Mexico sand. Once I cleaned the condenser out, it was much better. I think this ended up costing a compressor however, as it makes quite a racket.

It may be good to check the front out. Make sure you don't have an excessive amount of damaged condenser fins, nothing is built up between the radiator and condensor, and that the fans are working properly up front.

I don't think it'* the only issue, but if there is multiple issues it could be one of them.

Also make sure your A/C clutch isn't slipping.
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Old 06-15-2018, 11:57 AM   #10  
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Just a quick update. I added approx 8oz of freon to the system. Vents are now cold with low pressure 38ish and high pressure 195ish. I did find some evidence of oil residue on the dryer fittings, so I suspect a small leak there.
I'm leaving it alone for now, will repair leaks as needed later.

Thanks for the replies and help.

Joel
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