I got a re-chill kit to inject some Refrig into the low pressure port of my '99 Escort today. Before trying to recharge, I checked the pressure with the guage. I started the engine, turned on the A/C to max, and installed the guage hose to the low pressure port. The needle swayed back and forth around 50 psi, then SHOT up to the red to 80 psi and blew the gauge attachment off the car! The needle had pegged at 80 psi. What could possibly cause this to happen?
I won't turn the A/C on now until THIS gets fixed. I noticed the A/C would run well for a minute, possibly two minutes, then be gone and feel just ambient air coming from the vents. Then it would come back after more rpms were given to the engine.
Did the compressor cycle off prior to the pressure increasing?
Perhaps your system is overfilled?
FYI - You need to look at the factory service manual specifications and there should be a chart for what the low/high pressures should be for different outside temperatures and the compressor running. The pressures of both will increase with higher outside temperatures.
If you want to fix things right, you can order a factory service manual set of books from your dealer (many times 4 books to the complete set.)