Stumped on A/C - opinions appreciated

[EarlD]

1995 PA basic. A/C working fine, next trip nothing but warm air.

Put VAC on low side and found there was a very small leak. Shouldn't but put 3 oz can of stop leak in and 24oz R-134A, for 27oz. Manual calls for 2lbs (32oz).

Put gauges on low and high. Low reading about 68. Same with high, 68. From researching that should mean there is enough refrigerant in the system. (????)

Started engine and low drops to about 15 when compressor kicks on and climbs to 45 when compressor kicks off. As compressor kicks on, high goes to about 130 and drops to about 90 when compressors kick off. From everything I've read this indicates the compressor is working.

However, two things are happening:

1. The compressor stays on for about 3 seconds at most and kicks off. This would indicate low refrigerant but as I said about, from what I have read if the gauges stay about the same with the engine off, the refrigerant is ok. I also put 27oz of refrigerant in the system already.

2. A/C still blowing hot air.

I'm stumped. Any observations would be appreciated.

 

[kingpin]

I wonder if you might have a bad ac pressure switch kicking your compressor off each time it tries to kick on. I had to change one on my GM truck. Cheap and easy to change. Just a thought.

 

[MelsRegal]

which manual told you 32 oz? I found a site listing 39 oz.
what was the air temperature when you got the 15/130 reading?

 

[EarlD]

which manual told you 32 oz? I found a site listing 39 oz.
what was the air temperature when you got the 15/130 reading?

I got the 32oz from the label under the hood - actually the label said 2 pounds. Temperature was in the 78 degree range.

 

[EarlD]

I wonder if you might have a bad ac pressure switch kicking your compressor off each time it tries to kick on. I had to change one on my GM truck. Cheap and easy to change. Just a thought.

That is a thought, but even with that, I would assume that if all else is ok, as quickly as the compressor kicks back on I would think some small amount of cool air would come out of the vents - it is all hot. Not knowing anything about A/Cs, however, the compressor may have to run for a period of time before it will cool any at all.

 

[MelsRegal]

generic pressure charts for 80 degrees show readings of 40 to 50 low and 175 to 210 high.

 

[2007LucerneCXL]

You may want check this site to see if there is additional information on a fix.

The Automotive Air Conditioning Information Server

 

[EarlD]

You may want check this site to see if there is additional information on a fix.

The Automotive Air Conditioning Information Server

Thanks for the link. Some good information there. One thing that I did learn from the site, which conflicts with another site, is that as in my case the low and high pressure with system off being at 68 "does not" indicate there is enough refrigerant in the system but rather that there is refrigerant in the system. The other site stated that the same reading on both gauges indicated there is enough refrigerant.

That could explain the cycling on-off of the compressor - not enough refrigerant even though both gauges read the same at 68.

 

[HotZ28]

Static pressure readings should be about the same as ambient temp under the hood. If you are testing @ 80° F, both the high & low side should be about 80 psi. Of course, if the engine is, or has been running the under hood temp would be higher, so therefore you would have higher static pressure. I would add enough refrigerant to get the compressor to operate continuously with the AC set on max cool & fan on high speed. Once you accomplish that task, you can then test the low & high side pressures with the compressor running.