Stuck in 2-5 MPH/stop and go traffic for 40 minutes leaving (hot) Las Vegas on Sunday, the AC suddenly started blowing really hot air. Turned the Air Conditioner off for about 10 minutes. When we turned it back on, it blew really cold air, and ran OK for about 30 minutes, then started blowing really hot air again. Turned it off for a few minutes, and when we turned it back on it worked normally all the way home: about 5 hours. It worked OK yesterday when I was running local errands; about 30 minutes of driving.
Any guesses as to what would cause this?
Should I bother to have anything checked, or just wait to see if it ever fails again?
'97 Express Van 1500, 5.7 Vortec, conversion van.

 

Could be the clutch on the compressor. Or maybe the coolant is low, and low compressor RPM could cause loss of cooling...

 

Coolant level is OK. There have been a few times the AC was working but didn't seem to be as cold as usual. I guess I'll have to take it to a shop.

 

Not engine coolant, i meant the R134 in the ac system.....

 

It could be a vacuum problem. The doors inside the vents that direct airflow work on a vacuum, The one that directs air through the heater core sounds suspect to me.

 

I don't have a way to check the refrigerant level and don't know where to start looking for hoses to open the doors. How much labor should I be ready to pay for? Would 1 hour be enough?
I had the compressor, drier, orifice and high side shrader replaced about 4 years (2200 miles) ago.

 

Some shops offer a free ac service inspection. However as Wolfman says it could be a blend door actuator. Maybe even the ac dash control unit acting up. Its all electronic now on that van.

 

I wouldn't bring it to a shop unless the problem is actually occurring at that time.

 

Guess I'll wait until it quits. The AC dash control is 3 *****: blower speed, temperature, and doors (max AC, AC, bi-level, vents, defroster). The AC controls had not been changed when the AC quit; we had it on them same settings from the time we started until we got home many hours later.

 

Do a search. there was another thread about replacing a blend door actuator. I think its a servo motor. You may have a similar issue.