Model: Sierra 1500
Engine Size: 5.3l
Refrigerant Type: R134A
Ambient Temp: 90 F
Pressure Low: 85
Pressure High: 400
Country of Origin: United States
Please help,2004 GMC Sierra 1500 5.3l AC blows good and cold in the mornings. In the afternoons, a different story. As you drive, compressor kicks off. Put guages on, low side 85 psi high side 400psi (way too high). Replaced drier,orffice tube,flushed condensor, evaporator, and all lines, thinking a possible restriction. Fan clutch seemed weak, replaced. Still having the same problem. Is it my compressor???I ask because morning operation is normal. Low pressure switch replaced also, and refrigerant charge is accurate. Can't figure this one out.
My first guess would be air contamination (neglecting to evacuate before charging). Could be overcharged with oil, flush solvent residue, or condenser restricted (has the compressor ever failed?) Compressor making 400 psi means that it is good. You don't get any cooling with 85 psi low side, makes me question if the reading is good.
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