Defroster Duct Doesn't Blow

[75sierraclassic]

Well its starting to get a little chilly in the mornings and I recently noticed by defrost vent isn't working. What do you guys think is the most likely culprit? The hot/cold lever works, the A/C still turns on, it just seems that some of the dampers aren't working that redirect the air to the defroster vents. Vacuum leak somewhere, bad diaphragm, vacuum switch? If the hot / cold lever still works does this mean that the vacuum switch is good and its a diaphragm or vacuum leak somewhere?

[STOCKISH]

There is a vacuum line under the hood that is most likely unhooked or split. Mine is right behind the carb and hooks to a manifold vacuum source. Take care.

[77gmcjoe]

I had trouble with no air blowing out of the defrosters on a couple of different trucks, one time it was a bad vacuum pod and the other was a rotted hose going to a vacuum pod. Unfortunately I had to pull the whole plenum assembly out from under the dash to get to both of the problems.

[75sierraclassic]

Thanks for the info guys, found a rotted vacuum line under the hood. She's blowin again

[STOCKISH]

Sweet, glad you got it fixed. Missouri will turn to Misery real quick with no heat.

[kelsfine69]

I was watching this thread hoping for ideas on mine. Mine all works but air bleeds from the a/c vents when on heat and defrost. Mayby I will wait till the core craters then I will pull it all out. i was hoping for an easy fix to a similer problem

[632bbc]

this may be a dumb question. . . but where does the vacuum pod get it's vacuum from? I found the line coming out of the cab but that's all. . . my heater is the same way. . no defrost or floor just blows out the vents

[77nomad]

There is a tiny kind of hard plastic vac line under the hood that gets engine vacuum. Mine is teed into carb base.