I concur on the pressure issue. But just to add, I've seen worn clutches do this- they get hot and can't hold engagement. Sometimes it's just a bad connection but usually it's a mag coil going soft.

450 high side is a result of only a few possibilities.

1) improper cooling fan operation. Condensors need alot of air flow, specially on hot humid days to relieve heat from the r134 and cause the pressure to drop.

2) some debris from a ruptured desecant bag : service bulletin 06-17-12) is loged in the orifice tube between the high and low sides of the system.
Easy to verify because the low side will pull down too low ( under 18psi while the high side is reading over 300)

My bet is insufficient cooling because you say all is well on an 80 degree day. Check the fan clutch operation.

Failing that, theres a service bulletin ( o7-3-10 ) on the wiring to the computer controlled fan clutch that rubs thru and stops the clutch from hard engagement. A clue is that thing above idle when fully clutched in should sound like a friggin jet suckin air thru the rad. If you know someone with a WDS tool, uit can be used to force the fan to engage hard so you can check it.

it sounds like a cooling fan issue, is it a elctric or a manual or a clutch fan.

Ok, I was out of town but back. I drove it yesterday. On the way to work (20 miles and 80 degrees) it was cool the entire time. On the way home after 15 minutes (100 degrees) It started blowing humid air then the air warmed up and stopped blowing cold.

It is a manual clutch. Now that you guys mention that, let me through something else in there. I drove the truck with the boat about 200 miles. Before it kicked off (the a/c) it started roaring like the fan clutch was locking up fully, then the a/c would turn off.

If you guys tell me what to check, I will check it and report back.

Busta, whats happening?? Its a little 24' fishing boat that the in-laws own and I borrow. Still got the airplane and it is expensive enough, although I will probably get something in the next year or so.

Well I misstated. The fan is a manual/electric and that was the culprit. It was a b***h to change too. All good now!

Thanks for everyones help.