AC recharge on 2000 GMC 1500 SLE V8 5.3L 4 x 4

[Cliff]

First we evacuated the system to -28PSI, (using manifold gauges & vacuum pump); 1 psi drop in a half an hour wait. Then using 2 can of duracool (each can has 6 oz – equivalent 17 oz 134a) which is a few ounces over what the sytem called (29oz). We saw about a 10 degree C drop immediately and then a two degree rise when putting in the second can. We thought we might have added too much so we bled off the system from about 220psi to 210 psi. This affected no change in temperature. While filling I noticed that the low side was cold but the high side was hot behind a crimp in the line at a union between the high and low sides (expansion tube with filter has what looks like a crimp in it). We changed the compressor and accumulator before we did the recharge. We were expecting a greater change in the ambient and cooling temps. At the coolest we reached 12 degrees Celsius. Then we continued to add refrigerant and temp started to rise to around 14.4 degrees. The ambient temp was 20.6 degrees Celsius. What did we do wrong?

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[Jameson]

So is what you are saying the temp from the center AC vent was 54 degrees F (12C)??? The ambient outside temp was 68 degrees farenheit?? You were able to hold 28 inches vacuum for 30 minutes? was that with a vacuum for 30 minutes, or vacuum for 10 and sit for 30?

these details are important. you should vacuum for 10 minutes, then let it sit and monitor the gauges to see if you lose vacuum. 29 inches or 28 inches would be acceptable and prove you have no major leak. if there were no leak, it sound like you have a restriction somewhere if the temp is higher than what it should be.

did you flush the system and change the orfice tube?

[Mike]

What is your low side psi? Do you have any condenser blockage behind the grill? Is your radiator full of coolant? A cold low side line and hot high side line is normal…typicaaly, if you have an orifice blockage, your high side psi will be high.

[Author]

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