A/C Experts?

A while back I found out the reason the A/C wasn’t working on the F350 I bought back in January. For whatever reason the wires were cut and the connector plugs where missing to the high pressure switch and the compressor clutch. With the help of forum members I traced out the wires and bought new connector plugs. This past weekend I tried it out for the first time and it works. It blows really cold air until I get a few miles down the road and then the clutch disengages. If I turn it off for a few minutes and then back on, it works. I’ve checked the air gap on the clutch and it is within specs. I don’t have a gauge for the high side pressure but I do for the low side. At 82 degrees ambient air it is reading 45 psi which is smack in the middle of green zone for that air temperature. Does anybody have any ideas, one of the pressure switches maybe?

Operation and then shut down...  high pressure cut off comming into play.  Wager oriface tube plugged with black death.  Internal hose lining deterioration.  New oriface valve will cure problem temporarily.   Might be a year or more.  New hoses, dryer, system flush most probable cure for long term.

I was thinking along those same lines, because it doesn't do it at idle. But when the rpm increases I think it's building too much head pressure.

Check the pressure while running the engine at cruise rpm and see if it ramps up. What was high side reading at idle?

kim wrote:Operation and then shut down...  high pressure cut off comming into play.  Wager oriface tube plugged with black death.  Internal hose lining deterioration.  New oriface valve will cure problem temporarily.   Might be a year or more.  New hoses, dryer, system flush most probable cure for long term.

My bet is the fixed orfice is plugged or the dryer is shot. Both cheap fixes. Make sure the evaporator is not plugged up with crap too. The low pressure switch could be running the compressor too long as well.

My 94 F150 had a similar problem and it was simply a bad the switch... So check it with gauges while cruising...

Turns out it was a worn out A/C compressor clutch and the bearing inside of it was about to seize up. While they have it in the shop I asked them to check out the front suspension and steering. It didn't quite feel right, it wandered a little bit and turning a corner sometimes you could hear a "pop". All of the ball joints and rod ends are toast $$$$. I told them to fix it all, I couldn't drive it to TX like that.