what would cause the functions to go crazy??? if i turned on the a/c controls to a/c or vent it goes through the defrost...what would cause that???? does the controls cause that???? whatever helps thanks....
The doors in the heater / a/c box are vacuum controlled. The back of the knob has a few small hoses running to these door actuators. Maybe you have a vacuum leak somewhere that's causing this. I have a leaky lockout seal on my Superduty that causes this same problem if I have the truck locked into 4 wheel drive.
divit250r is right - there's a vacuum line that comes off the tee by the brake booster and runs along the back of the engine bay and goes into the firewall by the heater hoses on the passenger side.
divit250r is right - there's a vacuum line that comes off the tee by the brake booster and runs along the back of the engine bay and goes into the firewall by the heater hoses on the passenger side.