'98 Park Avenue - AC low pressure too high

[shrydvd]

1998 Buick Park Avenue Ultra

Issue started with no cold air. In the past year I have had issues with that & have added stop leak and freon. A couple times I again added freon when it would start not working again. The last time, was several months ago & it has held quite well.

I thought I needed to add Freon again but when I put the Walmart gauge on, it showed in the red.

From there I have tried the following:
I went to AutoZone & got a manifold gauge set. Both high & low pressure registered about 88 psi (static). I honestly don't remember what it was with the AC on.

I went back to AutoZone & got a vacuum pump. My thought was that maybe all the crap I was putting in there in the past caught up to me. So, I ran it down to -27. I had bought 3 cans of freon & one 8 oz bottle of PAG 150 oil (book called for 36 oz freon & 8 oz of the PAG 150 oil).

I read how to put the middle (yellow) line in the bottle of oil & open the high side valve to suck the oil into the system, which I did. Then, using my Walmart gauge again, I started to add the freon but it again went into the red.

Observations & things I have tried (besides the above) are:
1. The clutch does not kick in.
2. I shorted the relay which did cause the clutch to kick in.
3. I measured the voltage on the connector to the compressor & it showed something like .4 volts? I thought this was the problem until I jumped the relay & it worked.
4. An issue I keep seeing come up is the low pressure switch. The trouble is, I can't seem to find that. There are multiple places that tell where it is, but I must be completely blind because I can't find it.
5. I also removed (will buy new ones tomorrow) the cabin filters & my goodness, those things were disgusting.
6. I have checked all the fuses.

My question then is, does all of this sound like it could be the low pressure switch? If so, can someone please send me a picture or something that will tell me where it is on this vehicle?

Thank you all in advance for any guidance and/or help you can give me.

 

[HotZ28]

Sorry for the delay getting back to you! You could have a bad pressure transducer. but apparently have a system flooded with oil, or the control valve in the compressor is sticking with all the stop leak you have added! If the original oil was not drained/leaking from the system, you should never have to add oil unless the compressor & accumulator were replaced! There is not a separate LOW pressure switch, it is a traducer located on the compressor manifold/line next to the compressor that monitors both high/low side pressure and sends that info to the PCM to activate the clutch. The attached may not be vehicle specific, but it does describe how the GM transducer system works.