See if I have summarized this correctly. MAX at 1400rpm: (rpm at 55mph) 25/210 (Engine cold) NORM at 1400 started at 30/250 and gradually climbed to 40/325 So as the car warms up the pressures rise, especially the high side? Pressures always read when clutch engaged? Can we get complete set of read...

I am not familiar with your car's AC controls and exactly what they do. For that matter we do not even know what car you are working on, you never said. What repairs have been made and why? In any event, try to find a setting that does not allow outside air in. Can't think of more foolhardy enginee...

AC draws some outside air when in NORM. Is this not correct? Higher evaporator temperature due to outside air results in warmer refrigerant/higher pressure. Is this not correct? I used 1400rpm because that is cruising RPM. The later, higher reading in MAX was after everything was warm. Higher system...

Got the new gauge. It is as accurate as the high pressure gauge. Now curious about the wide splits between low and high pressure readings. Ambient starting out 80°F. Outside air and vehicle in the shade. 80psi static pressure. Pressure switch opens at 25psi, closes at 45psi. On MAX at 700rpm idle: 2...

Never trouble trouble until trouble troubles you !!! What's to sort out on that truck????????????? I hear ya! The 1986 Ford truck is now a R-12 to r134a conversion. I went to adjust the low pressure cut off because of freezing. The switch, seat of the pants adjusted down from 40psi, was too set low...

tbirdtbird wrote: ↑Mon Sep 13, 2021 2:10 pm Maybe switched the hi and low sides by accident

That sounds like it.

Ordered a new gauge. After it comes in, I'll be back for help sorting my truck's AC. Which is cooling great by the way.

Actually, he used it on a thirty-five year old R22 unit on his boat.

FWIW: The gauge is toast. I gave the Bourdon Tube a little nudge where I could dial it in to zero. Opened the can of r134a I had used last and high side went to 75psi, the low side to 100psi.

New gauge is cheap.

It can only be adjusted down to just below 40psi. I set it at 40 and subtracted that from read pressure. Of course I'll try the pliers.

I was actually just wondering what caused it to tweak so badly.

So, I loaned out my beloved gauge set. I know, bad move. The set was given to me by a friend thirty-five years ago. Probably one of his older sets then. (He was an HVAC technician) When I went to work on my truck today, I noticed that the low pressure gauge is resting at 45 psi when it should read z...