Mechanics

HEATING ISSUE,122,000 MILES 4.3 6CYL

1990 GMC Safari

Heat blows through defrost vent, but when I try to switch to optional vents I get nothing like the vents are not hooked up. All the blower speed settings work, and I still receive heat just not through any other vents.
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Samarian05
March 15, 2007.



There is a small black plastic vacuum line that is broken. Pop the hood, the line starts at the plenum on your left, the vacuum line goes across the engine to the drivers side, it will be broken.I like to replace it completely with vacuum line instead of the plastic.

Tiny
Jack42
Mar 16, 2007.