AC Problems High Pressure Spike at Start Up
99 ranger 3.0L automatic. I put a set of gauges on the ac system at 78 degrees static pressure around 82, which seems good.
I start the truck up and switch on the compressor within a second the high side gauge pegs out and the compressor dump valve opens.
Then the pressures fall to right where they should be, around 40 low and 165 high at idle. I can let it set there and run for 30 minutes no change in pressures and the vent temp is about 49 degrees. I can switch the compressor off wait a minute switch it back on no problem pressure right where they should be.
Shut the truck off come back 30 minutes later and it starts all over again with high pressure spiking and then normal.
Any ideas why it would spike high side on start up and then run normal?