Automotive Air Conditioning Information Forum (Archives)

ijroorda on Mon July 01, 2013 10:10 AM

Year: 1997
Make: Oldsmobile
Model: Aurora
Engine Size: 4.0L
Refrigerant Type: R-134a
Ambient Temp: 80
Pressure Low: 45
Pressure High: 260
Country of Origin: United States

I have had this car for about 4 years now; it currently has 205k miles on it, original compressor as far as I know. The A/C has always worked OK, if not as well as some other cars I've owned. This year it was not blowing as cold; the evaporator inlet was cold but the outlet and accumulator were warm so I assumed a low charge. I have a friend who works at a tractor shop and has access to a recovery/recharge machine, so Saturday morning we hooked it up and recovered the charge. We recovered 1lb 10oz; system capacity is 2lbs so it was indeed low. It held a vacuum so we went ahead charged it with 2lbs; at idle I was seeing about 35psi low and 160psi high at 75° ambient temperature with vent temps at around 45°.

My wife ran an errand Saturday evening and when she pulled in the driveway at home I could hear something clattering under the hood. I turned off the A/C and the noise went away, turned A/C back on and it gradually returned. I hooked up my gauges and was seeing about 45psi low at idle; the high side needle was oscillating very rapidly but was centered at around 260psi.

I'm pretty certain that the clatter/chatter noise is coming from the compressor and not from the belt tensioner or something like that. I assume my compressor is on its way out, but I'm looking for advice on anything I can do to verify that before I replace it. I haven't seen the gauge needle bouncing like that before - what might cause it to do this?

Thanks for any help!

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Isaac Roorda
Pella, Iowa

GM Tech on Mon July 01, 2013 2:37 PM

one or more broken suction reeds- very common-

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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......

ijroorda on Mon July 01, 2013 11:37 PM

Thanks for the info. What can I do to verify this before I replace the compressor?

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Isaac Roorda
Pella, Iowa

GM Tech on Tue July 02, 2013 7:41 AM

Does the compressor hub (not pulley) turn very easily- little or no resistance? Are there stainless steel chips in the orifice tube screen? both are positive indicators of suction reed failure..

-------------------------
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......

ijroorda on Tue July 02, 2013 9:23 AM

I'll pop the belt off and see how easily the compressor turns. Opening the system to check the orifice tube screen will have to wait until I can get the car into my friend's shop again - probably next week. Thanks very much for the info.

EDIT: nevermind, I suppose I can spin the compressor hub without pulling the belt. I'll take a look tonight.

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Isaac Roorda
Pella, Iowa

Edited: Tue July 02, 2013 at 9:32 AM by ijroorda

MrBillPro on Tue July 02, 2013 9:40 AM

Not really an auto a/c guru here, I do commercial and residential. Is it possible he pulled some/lot of the oil out when he recovered, and just put refrigerant back in, less the needed oil?

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Don't take life seriously... Its not permanent.

Edited: Tue July 02, 2013 at 9:40 AM by MrBillPro

GM Tech on Tue July 02, 2013 10:19 AM

No- can only do that with a/c running and sucking refrig out the liquid line discharge pressure port...

-------------------------
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......