Help with HVAC issue

[Keith Seymore]

2004 Silverado 2500 HD with Duramax.

Auto HVAC controls.

The issue is that with the controls set cooler than the outside ambient temperature the system will occasionally change itself and start blasting insanely hot air out the driver's RH vent.

Last summer it was fairly infrequent. This year it can happen every 10 or 20 minutes during an extended road trip.

Recycling the ignition will we restore normal operation. I thought maybe if I placed the system on manual fan operation, rather that auto, that would help but I don't think it makes a difference.

After doing a forum search I performed a system reset, per the attached. That maybe(?) helped for a while but yesterday while driving over a three hour period it was doing it every 10 or 15 minutes.

My next step is to replace the HVAC control head, unless you guys have other ideas and talk me out of it.

Thanks in advance -

K