A/c heater only blowing through defroster vents
I had some work done on the high pressure oil pump, and now I get hot air in the cab. when I turn on the A/C it blow through the defroster. No matter were I try and send the air it goes to defroster. The vac continues to run all the time. I disconnected something that in bolted to the right fender by the vac pump and a black box now the vac will stop and I can change to all vents. I tried to change that part on a friend truck that his work just fine and it went back to doing the same thing. If I unplug it all works fine. any help with this problem Thank you!