Dash AC Blows hot air under load
The Dash AC works fine when at a idle or the engine is cool, but going down the road or when the engine is warm or the engine is under load then the Dash AC blows hot air no matter what I do with the controls. There is a valve that is controlled electrically in the heater hose that is supposed to shut off water to the heater core when the Dash AC is on. I am wondering if that valve is defective and keeping hot water in the heater core all of the time. There is a vacum pot That controls a Door or flap transferring air from the AC to the front vents in the dash. I can find no vac leaks. any help or suggestions would be appreciated. The chassis is a ford F-53 and the engine is a V-10 30 valve.