I'm having an intermittent AC problem. The other day, after driving 20-30 minutes, outside temp around 50F, inside temps set around 70, the AC took off to max fan speed and cold temp. Turning down the fan speed (AUTO off) did not affect cold temp; raising set temp did not affect cold temp. Returning to AUTO returned max speed (cold). The system returned to normal after 15-20 minutes. this has happened twice previously in the last 6 months or so, although about a month ago I drove uneventfully on a 120 mile round trip, temp in the 60's. I'm currently only driving the car 1500 miles/year, so not many opportunities for it to happen.

Is there some module in the car that is a likely cause? Since this is infrequent and has only occurred after driving some distance, a trip to the dealer may result in a bill for diagnosis, and "symptom could not be duplicated". Somebody mentioned cabin temp sensor on a thread awhile ago. Could this be the problem?

I've also noticed for many months that the dash vents blow outside air when the car is started, rather than waiting for for the engine to warm up. Related, or normal operation?

Thanks for any advice...