My question is,what can cause a volvo big truck a/c to work when you first start your day?.?

Question

But after about one in half hour into your run the a/c starts blowing hot air.I must have drove 122 miles,i got to my terminal and i shut the truck off.It was hot,very hot on 6-27-07 in roanoke va.I waited about 30 to40 minutes and a/c felt better,it also rained during this time.After one hour or so it seemed to work fine.My company doesn't believe this can happen,i need some professional feed back.They think i made this up.Thanks Donnie Fontaine Sr.

Answer 1

If the AC would be low on refrigerant then it wouldn't be able to work correctly for 1 and a half hour, it would cut in and out every 10 seconds.
Since you mentioned that it was raining that day, the humidity was probably within 90-100%, which could have caused the evaporator to freeze up, creating a big block of ice around it preventing it from cooling down the air in the cab of the truck.

Then after 1 hour the ice had melted off the fins of the evaporator enabling it to cool down the air again.

It is very possible that the system had been overcharged (too much freon), not allowing the low-side pressure to drop low enough to dis-engage the compressors clutch (controlled by the low-pressure-switch) to prevent evaporator-freeze-up, creating more and more ice that blocked cool air to get through.
.

Answer 2

From these symptoms I would say it is low on refrigerant. You need someone with a set of a/c gauges to check the pressure.