It works fine in the morning, but on the way home, after about 10-15 minutes, it goes warm. On cloudy days, not as quickly. I hooked up my gauge, with a fresh can of freon, to see if maybe it was low. It was in the 'good' range, and it didn't take any. Yesterday, after it gave out, I pulled in a parking lot, and put the gauge on again. It was in the red, about 100 psi! Also, went on the highway to a job today, at least 20 mins. or more, and it stayed cold the whole ride, and heading to Lowe'* around noon, also good, until I got back into the neighborhood. Truck recently turned 200K, 50K by me, and it'* been solid & reliable.

I'll add that today, mid 90s, left to go back to the shop around 2 pm, peak heat. I turned the fan all the way up, and it only lasted 7 minutes! Seems like something is getting hot, and cutting out the compressor.

Does the air flow get less? If so, the evaporator may be freezing up.

I wonder if it is over charged.

It would be good to know actual pressures and corresponding ambient temperatures.

No, it stays consistent.

Well, it'* still factory specs, at least for the 5 years I've been driving it.

If it has an issue, it probably is not at factory specs. 17 year old truck is is probably not at factory specs. Does your gauge have actual measurements on it?

Need to get gauges on it.