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I'm new here my 98 GMC Savana 3500 isn't

MJEFFERS

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Ok not sure where to post this but I'll try it here.

Got this old 98 savana last summer and the AC was not working. I've been educating myself as best I can on youtube and tried changing out a leaking compressor. I got it all changed, added the recommended amount of oil to the compressor, pulled a vacuum on the system and refilled with the recommended amount of R134A. Miracle of miracles I'm getting cold air out of my vents now... and after a few minutes the whole cab is cool!

BUT...

When I turn off the engine I hear a hissing sound near the dryer that sounds like it may be coming from the evaporator. I put the gauges back on the system and what I notice happening is a equalization in pressure between low side and the high side. Is this what is supposed to happen? Maybe? This is the sound I'm hearing. Listen yourself here it dissipates after a few seconds.


Is this normal?
Thanks in advance if anyone has an idea what this is.
 
Yep, normal. All a/c systems do this if you shut it off while operating.

The compressor is a hard point of selection high side to low side by it being a pump.

The orifice/ expansion valve point is another point that separates high from low pressure. When the refrigerant stops cycling because of he pump stops, now the high side equalizes (as you saw on gauges) between them.
That sound is the high side bleeding to the low side.
 
WELCOME to TTS!

I usually turn off the compressor a very short distance from when I plan to park just to let things cool-down and settle a bit. Maybe this is wasted effort, but it does seem like the system appreciates the effort when I go to restart a short time later.
 
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