You guys have probably seen this problem before, but I'm at a roadblock and have some questions.

I've been going through the vac system trying to get the heater working properly. It's stuck on defrost like I've read in numerous posts, however I've located all the leaks I could find. I have enough vacuum to operate the auto 4wd and there seems to be good vacuum at the selector switch for the heater, but it still won't operate the actuators. The actuator that switches between floor and defrost will move a little, I can set it to floor and physically force it to the floor position and it will stay, but if I switch it to defrost and back it'll drop but not return nor do I get any air out of the dash vents. Are those diaphragm actuators a known problem? Also, has anyone ever seen these trucks without a vacuum pump? I can't find one anywhere or even a rouge wiring harness or fuse designated for one.

Thanks

 

Vacuum pump? Not on a gas engine truck.
You may have a bad vac motor...Get a vacuum suction test tool and see if the motor works ok..These trucks don't have any issues with heater etc.

 

Thanks, that puts my mind at ease. I'll check that vac motor, it seems to have more resistance than I would assume.