2003 ford e350 handicapped conversion only blows hot air out the rear ac

There is an vacuum expansion tank next to the heater core that rusts out also. You will notice that the air stops flowing when the engine is under a load mostly at higher speeds and when you let off of the gas the air slowly starts flowing again. Shop charges over $1000 to repair.

I have 2 e350 vans and had that problem on both. In the rear AC, between blower and heater, there is a flap with a little hook. the hook is broken and the flap doesn't change position anymore. It very easy to fix. the biggest work is removing the panels. go to Ford dealer part and ask schematics of rear ac to locate and replace the part.

You will need to check the rear blend door actuator.