Originally Posted by Guapo XLT
thanks for the pointer. Where should i start looking for the leak? I swear i got the air to come out the main vents the other day on the fan set at MAX -1 notch. Once i went MAX it stopped again and only came out the defrost vents!!
If you pull off the passenger tire and splash guard, you will find the vacuum reservoir tank and from that you can follow all the vacuum lines to check for leaks. If you have the PVH 4x4 system, there will be an additional line between the reservoir and the PVH solenoid, and then from the solenoid to the wheel ends. The reservoir has a built-in check valve that I have heard can fail. I've also heard of the PVH solenoid failing and allowing vacuum to bleed off.
Here's another thread with information on the climate control air flow system:
https://www.ford-trucks.com/forums/s....php?p=2020808