Does anybody know the optimum low side presure. My unit is cycling on and off and I think I overcharged it. It was running up to 100 PSI and tripping out. I have let some out (I really don't have a clue what I am doing) and it is running steady around 70psi.

BTW, Ac is crucial as I live in Phoenix and its 114 today. ya ya its dry but so is your oven.

It's not a pressure that is critical it is the amount of R-134. The only way to make sure it's done right is to have a professional do it. Home A/C charge kits are nothing but trouble waiting to happen. Take it in and have them evacuate the system and install the precise amount of R-134 that is required. You'll save yourself a lot of headaches.

x2

I'm a commercial HVAC tech and I wont even deal with my own a/c on my rodeo. Mine cycles alot too, it was over charged when I bought it and I got it working better but I think there is air in the system. Sometime this year I plan to take it in and have them evacuate it then recharge with the proper amount.

Pressure depends alot on outside air temp and temp inside the vehicle so you cant really give a specific pressure and the range of temps/pressures is too wide to be of any use for guessing the proper charge. As an example here is what the FSM says for a '99 rodeo..


Normal Pressure:
At ambient temperature: approx. 25–30*C
(77–86*F).
At low-pressure side: approx. 147.1–294.2 kPa
(21.3–42.7 psi).
At high-pressure side: approx. 1372.9–1863.3 kPa
(199.1–270.2 psi).
You might get it close but can never get it right without weighing in the proper amount.

Also, the gauges on the home charging (aka compressor suicide) kits are known to not be very accurate.