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High side service port

thx1138v2 on Sat August 17, 2013 9:32 PM User is offline

Year: 1994
Make: GMC
Model: C1500
Engine Size: 4.3L
Refrigerant Type: R134a
Ambient Temp: 93
Pressure Low: 40
Pressure High: 210
Country of Origin: United States

This is my first DIY auto A/C job. I replaced the compressor, clutch, compressor switch, accumulator/dryer, clutch switch, and condenser with new white tube/orifice.

I may not have had to replace all of that but the switches were 20 years old and the condenser had about 1/3 of the fins on the passenger side were bent over closed and when I tried to straighten them some broke off and another spot was damaged where a bird went through the grill.

After flushing the system I drew 30 in Hg vacuum on the gauge and it held it for 15 minutes before I started charging. It was blowing cold with the readings above.

Everything was fine until I took the gauges off after charging the system when the high side service port was leaking. The refrigerant was not blasting out of the valve when it was charged but there was a continuous hissing and I could feel it.

I thought it was a schrader valve so drained the system to replace it but apparently it is not. It appears to be a black plastic ball. I can rotate it around with the end of a long, small allen wrench. It is in a fitting on the aluminum tube coming out of the compressor that has 5/8" hex sides on it. It looks like a two part fitting so I'm guessing it is what you call a Primary Valve. I can fit a wrench on the lower part and a socket on the top part but I can't get them to break loose. So am I mistaken that this is a Primary Valve?

I read somewhere that I could just put the plastic cap back on and that would hold the pressure and keep it from leaking. Is that right or is it going to leak over time?

The whole reason I started this job was that I had a slow leak at the compressor shaft seal behind the clutch that would have only gotten worse so I'm a bit dismayed after all of the work and money to still have a leak.

Since I can't get the fitting apart the only solution I see is to replace the entire hose and compressor block.

Any suggestions will truly be appreciated.

GM Tech on Sun August 18, 2013 7:53 AM User is offline

This site sells the valve assembly- it unscrews from the mount- this is a very common problem- Yes the cap will seal if it has the rubber washer inside- but it is always best to meerly replace the high side port. I stock about a dozen in my arsenal.

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......

thx1138v2 on Sun August 18, 2013 8:35 AM User is offline

Well, duh! I looked at it more closely this morning and I was putting 5/8" the socket too far down on the fitting so the 5/8" wrench was on the bottom of the base and the 5/8" socket was on the top of the base. No wonder it didn't come apart. A wrench on the upper flats near the top opened it right up.

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