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A/C works for 20 seconds and then gets warm

justin4you2 on Sat June 12, 2010 3:07 AM User is offline

Year: 1987
Make: Subaru
Model: GL
Engine Size: 1.8
Refrigerant Type: R-12

Hi. Here is my problem. When I turn on my A/C, the compressor kicks on along with the cooling fans. Everything works great for 20-30 seconds. It is cold during this time too. Sometime after that 20-30 seconds, the vent air starts getting warm. The compressor is still engaged when it gets warm and the cooling fans are on. I put a set of gauges on the car to see what is happening. Initially, when the vent air is cold, the high side reading is good along with the low side reading. But when the vent air becomes warm the high side and low side readings come together and eventually settle at the same reading. Keep in mind that the compressor is engaged this whole time and the cooling fans are running. When the vent air gets warm and the high/low side settle at the same reading, the compressor gets noisy and acts like it is not under any type of load. If I shut off the A/C and start it back up, it still stays warm. Only after the car has cooled down for a couple of hours will this whole scenario start over again. The system is fully charged with R12 refrigerant and there are no leaks in the system. Could this be an expansion valve issue or an internal compressor issue? What else could be causing this? I have no idea where to go from here. Any help is greatly appreciated!

Justin

TRB on Sat June 12, 2010 11:47 AM User is offlineView users profile

What are the pressure readings? Saying they are good is to vague of an answer.

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justin4you2 on Sun June 13, 2010 12:20 AM User is offline

Ambient temperature: 80 degrees
Low side: 35 psi
High side: 180 psi

These are the values BEFORE it starts blowing warm air. As it starts blowing warm air, the high side drops and the low side rises. The compressor is running the entire time and the cooling fans are running too. Hope this info helps. Thanks.

Justin

GM Tech on Sun June 13, 2010 8:28 AM User is offline

Sounds like internal blowby- inside the compressor- due to severely worn cylinder bores- is this a variable stroke compressor?-- it can cause the compressor to destroke if that is the case.

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

bohica2xo on Sun June 13, 2010 8:16 PM User is offline

It's a rotary vane compressor, and it sounds like it is done.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

justin4you2 on Sun June 13, 2010 11:35 PM User is offline

Thank you all for your help. Is there an additive I can add to condition the compressor internals to get a little more life out of it? Or is my only option a new compressor at this point?

Justin

bohica2xo on Mon June 14, 2010 2:00 AM User is offline

There is no such thing as magic in a can. Bad news, I know.

Has anything besides refrigerant ever been added to this system?

A reman compressor for that car is about 250 bucks. A junkyard compressor may not be as good as the one you have right now...

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

justin4you2 on Mon June 14, 2010 2:57 AM User is offline

Nothing has ever been added to the system, not even refrigerant. The car has been in the family since new and it has never needed work on the air conditioning. It has never leaked and/or needed a recharge. And as you can tell by the gauge readings, it still has a good charge. It's just unfortunate that this had to happen with the compressor.

bohica2xo on Mon June 14, 2010 10:20 PM User is offline

Everything wears out eventually. 23 years is good service from an A/C compressor.

Make sure you flush out the old (and very worn out) oil when you change the compressor. Flush the metal parts back to bare metal, and clean thew hoses well. Replace the dryer, and any hoses with mufflers in them.

I would keep the car R12, unless you plan to upgrade the condensor.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

justin4you2 on Thu June 17, 2010 12:01 AM User is offline

Hi. Just wanted to post an update on this problem. Before I spent big bucks on a compressor, I took the car into a local A/C shop to be looked at. They found out that it was not the compressor that was bad, but the expansion valve instead. They said when the A/C would start blowing warm air, they could tap on the expansion valve and it would start cooling again. They replaced the expansion valve and now the car is cooling perfectly again! They recaptured the R12 and put it right back in the system. I wasnt out any money for refrigerant...just the labor and the cost of the expansion valve. Just wanted to let everyone know...

Justin

bohica2xo on Thu June 17, 2010 1:39 AM User is offline

Interesting. You described a system that equalized when running, but they claim a closed TXV.

If the TXV was closed, your high side might have dropped some, but not far as the charge was sequestered in the receiver. The low side however would have gone low, perhaps even into vacuum. By your description it went high...

Good you got it fixed, but keep an eye on that compressor. What you described was a typical sticking vane problem - noisy & no pump.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

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