2nd Gen Non-Engine/Transmission Only defroster vents work

[JGrover]

Changed out the fuel lines, and I know i poped off a vacuum line. Service manual says theres one on the intake? Got the boost gage, the afc housing. The only one I know that works the ac/heater controls is coming of the vacuum pump? Cruise and vacuum pump hoses go to firewall and goes through the firewall on passenger side of truck. everything looks hooked up. No open ends anywhere.

 

[Joe G.]

The vacuum line to the heater/AC control goes through the firewall where the heater pipes are. If there is no vacuum to the control all you get is the defrost vent. The vacuum line can melt closed because of the exhaust manifold. There is a connector there. Mine had melted closed inside the connector so you need to inspect that too. Here is a picture of the heater/AC vacuum pipe going through the firewall at a heater pipe. If it's not melted then look at the connections under the dash, heater side first, to make sure they are all connected.



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[Chasweaver]

When I had the same problem I started at the vacuum pump and pulled apart and reatached each fitting all the way to the firewall and I guess I got lucky as it has worked great ever since. Charlie

 

[rono]

When mine did that, it was the one at the vacuum pump.

Ron