I was hoping to figure it out on my own but no prevale... it the heater control run by a vacuum line or is it electrical? i take it it is under the dash because i couldn't find it under the hood.and is there a diagram anywhere for it thankx to anyone who can help

 

Manual controls or automatic? With both, there is vacuum controlled valves in the HVAC system, but with the automatic temperature controls, there is a lot more electronic interaction controlling the vacuum operated valves.

Letting us know what your truck is doing would help...

 

i have hot and cold and the ac works the problem iam havin is that it wont change out of the defrost ..i try heater ,vent, blend and still goes threw the defrost.. i was guess it was a vacuum line

 

Yeah, sure sounds like a problem with the vacuum supply to the HVAC panel.

Schematics depend on my first question.

 

oh sorry forgot about that i have manual control... thankx again

 

Have a look at this: