climate vents stopped working

[Barry E]

Had a problem with auto fuel shut off so I was fooling around down in the passenger floor/firewall area. Apparently the trouble was the fuel filter which I subsequently changed. Truck runs fine now but the vents will not work properly. Only the defroster or the foot vent will work. The dash vents will not. I made sure everything in the fuel shut off area was ok...no vac hoses or anything seem to be amiss. Any suggestions would be appreciated.

 

[Dan Long]

You've got a vacuum issue. My truck switches to the defrosters under heavy load or acceleration (low vacuum times), I just haven't had a chance to track my problem down yet. I believe there is a vacuum bulb down there around the fuel pump shutoff.