Cold then Hot

[aircrewjake]

I have a 04 Chevy Tahoe. When driving my truck will go from full cold to full hot with not input from myself. I have the dual climate control heater switch. I think it may be a solenoid that directs flow into the heater core. But I am not entirly sure. When I stop turn the car off and turn it back on it works in cold again. Has anyone heard of this and do you know what is causing if?

 

[Yang1815]

Hmmm I've had similar problem where it's all heat after the battery's disconnected. I'd disconnect and re-connect just to see if it resets.