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Low A/C Pressure


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Posted

Thanks! That's the price I was hoping for. I know they're not on sale locally and I didn't think to check online. They'll PM their online price, so I'll probably pick one up this weekend. If I'm extra lucky, they'll send me another 10% off coupon in email.

  • 5 weeks later...
Posted

I finally picked up a manifold gauge set and took some readings.

 

Initial (engine off, engine cold)

Low 73 High 75

 

Engine on, idle after 5 mins

Low 125 High 125

 

Engine on, idle after 10 mins

Low 144 High 145

 

After a few seconds at 3000rpm

Low 153 High 160

 

Off immediately after run

Low 110 High 110

 

Looks like my low side is always equal to the high side. Any ideas?

Posted

Shawn, what was the temperature outside when you took these readings? Judging by the first reading, I would think in the neighborhood of 70*F if I'm remembering the proper ranges on the psi/temp charts? Looking at those readings, I think they're indicative of a failing compressor or compressor clutch being that the low pressure side is reading too high and the high pressure side is reading low.

Posted
I finally picked up a manifold gauge set and took some readings.

 

Initial (engine off, engine cold)

Low 73 High 75

 

Engine on, idle after 5 mins

Low 125 High 125

 

Engine on, idle after 10 mins

Low 144 High 145

 

After a few seconds at 3000rpm

Low 153 High 160

 

Off immediately after run

Low 110 High 110

 

Looks like my low side is always equal to the high side. Any ideas?

 

It doesn't look like the compressor was running at all. Could you verify that when you turn on the AC, the compressor is indeed spinning? If the compressor was running and everything was in good working order, you should have seen pressures around 28-35 on the low side and 180-250 on the high side.

Posted

Yeah, ambient air temp was probably around 70.

 

Yeah, the compressor was running and clutch was engaged. Probably a bad compressor?

Posted
Yeah, ambient air temp was probably around 70.

 

Yeah, the compressor was running and clutch was engaged. Probably a bad compressor?

 

Unfortunately, that is what it looks like.

Posted

Is it worthwhile to rebuild a compressor, or is it better to just pick up a used one?

 

I'm guessing 94-96 3.4 compressors will work, but will anything else interchange?

The car is R-134a.

Posted
Is it worthwhile to rebuild a compressor, or is it better to just pick up a used one?

 

I'm guessing 94-96 3.4 compressors will work, but will anything else interchange?

The car is R-134a.

 

It would be cheaper to buy a new one but if you have a working one you can use then that would be just as good. Just make sure all the mounting points are the same as well as the manifold connections are the same.

Posted

Is there any big difference between a R-134a and R-12 compressor?

 

I think the exterior is the same as 88-93, mainly because 94 3.1L Luminas used the same compressor.

Posted
Is there any big difference between a R-134a and R-12 compressor?

 

I think the exterior is the same as 88-93, mainly because 94 3.1L Luminas used the same compressor.

 

There shouldn't be any difference. Both compressors are the V5 variable displacement compressors.

Posted

Sounds good, that will give me a lot more possibilities.

The photos I've found look identical as far as the body itself. Will there be something in the seals that will require me to use ester oil rather than PAG?

The service manual calls for PAG, but I know retrofitted cars must use ester. I think because PAG attacks seals designed for R-12, but I'm not sure on that.

 

Is there any possible way the AC clutch could be spinning, but the compressor not spinning on the inside?

  • 4 weeks later...
Posted

UPDATE: A/C is finally fixed!

 

Turns out I wasn't using the manifold gauge set right - I was following EXACTLY the instructions that came with my Harbor Freight gauges which said to get readings with the thumbwheels turned counter clockwise (open). That's why it was looking like the compressor was bad.

 

With the wheels closed, I was getting readings of 70/150. I posted these readings on an AC forum and one of the experts told me to replace the control valve.

 

So I bought a cheap compressor out of a '99 Malibu from Ebay for $10, pulled the control valve out of it, and put the control valve in the 94 Cutlass. Then I vacuumed the system, added 2oz of PAG and filled with R-134A and now it blows nice and icy cold!

 

Anyway, it was $250 worth of tools and parts (vacuum pump, manifold gauge, freon, oil, assembly lube, etc), but very much worthwhile!

Posted

Glad to hear you got your a/c working Shawn!! I know I used mine everyday for the past week.

 

$250 is alot better than the $640 I spent to get the a/c fixed in the Regal 4 years ago. eeek!!!

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