I just tore into my dash to replace some burnt out insrument panel bulbs and when I put everything back together and started the truck it started hissing. I can't change where the heat comes from either. It always comes from the window defroster and heater vents at the bottom. The hissing is coming from the vacume lines behind the controls but nothing is cracked (I think) and I can't feel any leaks. Any advice?
You probably wouldnt be able to feel any leaks because it is vacum instead of pressure. If it wasnt doing this before you worked on the dash lights I would think that something got pulled loose or a line got a hole in it. You might want to check and make sure where the lines plug to the back of the heater switch is plugged in good. Good luck.
i have the same thing... i tore the entire dash apart and diddn't find anything, then i looked down, right next to the driver side ductwork(center of the truck bottom of dash) theres a relay? thingy, i'd look there first
It must be an eppodemic with these thing..mines a victim of that too, but if I put the controler between defrost and vent it dont do it and if i have it on defrost ( i get that) and the floor.. It always blows on the floor.
I fixed my controlls. All I did is remove the heater control and all the wireharnesses. I left the vacume tubes on and put the heater controls to off and wiggled all the lines until it stopped hissing. Then I put it to max AC and wiggled it untill it stoped, and so on. My controlls work right now.