Thanks for the tips Kyler! I’ll be sure to check on the bolts after it runs for a bit. Not currently driving the GT on the road, it still needs bodywork and paint.
Mine cools down to about 35-40° when it’s 80° outside.I vacuumed the system again today, although once I put the lines on again it showed that it held vacuum overnight. Then I slowly added a total of 1.88 lbs. of r134a. while running the AC. The inside of the GT was ~85 degrees, ambient temperature outside was about 72-75. The temperature of the vents on full cold setting was from 49-55 degrees Fahrenheit. Idle dropped from 1200 to 1000 when the compressor kicked on, so about a 200 rpm drop. Engine temp stayed below halfway.
High side while running was much lower than your readings, just under 150 psi according to the gauges I used; as was the low side, at 25 psi. I don’t recall what the pressures were with the ac off. It seems the high pressure drops and the low goes up when the compressor turned off.
Is my scale off and I undercharged it? It seems to cool ok.
I would still add more, unless you have another cooling fan your head pressure might be a little higher than usual due to the GT’s less than spectacular radiator fan. As I said when you get close to the optimum charge you’ll stop seeing the pressures vary so much. My guess with that low low side pressure is the compressor is short cycling too?
Sounds okay and as long as you’re happy with it.So I topped the system up a bit more, at about 70 degrees ambient temp the high pressure was 160, low was at 25. I know the low side is a bit low, but it cools well and I’m happy with it. So that’s pretty much it!
That’s the rule of thumb. That said, automotive A/C units typically have a protective pressure or externally mounted cut out switch on the low side that keeps this from happening hence the short cycling of the compressor. That’s why you almost never see an iced up coil when you gat a refrigerant leak, the efficiency just keeps getting worse until you get no cooling. I keep mentioning this, the compressor will keep clutching in & out if you don’t have enough pressure on the low side with this function.If the evaporator coil temperature is 32 degrees or less, don’t you run the risk of condensation freezing up in the evaporator? I read about that happening in the GM AC service manual.