That vacuum line originates at a T fitting at the vacuum reservior (about a 5" black ball) located near the right front inner fender, about 2" forward and right of the engine block. A larger tube supplies the vacuum from the right rear of the upper intake manifold (plenum) fitting. This tiny plastic tube is prone to drying and splitting in the area that is exposed to engine bay heat before it goes into the wiring harness loom, so give it a good look over there. Also, the manual valve in the controls gets loose from use and will loose vac there, I've made special and cheap kits to repair this. On my '95 Astro I had only 5" of vacuum at the fitting on the plenum, a new gasket brought it back.
Most all of the vacuum lines will start from the intake manifold in the rear..........
It's either the thermostat or the heater controls.
lose of vacuum to heater deverter valve.follow heater hoses from engine to heater core valve has two hoses in and two hoses out and one vacuum hose.vacuum hose gose to tee then back to engine other vacuum from tee controls heater switch defrost to floor heat knob. replace all of these lines about 6 feet will do it.now the bad, you must pull back the dog house about a foot divers side to remove one vacuum hose just do it the first time and both problems should go away.
heater sensor circuit Chevy astro 2000
can I get a diagram to replace vacuum hoses ona 986 chevy astro van
vacume line to the valve has broke off from manifold vac that goes to the switch
How do you change a heater core in 1994 chevy astro van?
Check for a vacuum leak or broken vacuum line first and if all is correct then you will need to check the a/c - heater controller..........
The heater resistor on a 94 Astro is located on the top of the heater box under the hood, it has a four or five wire plug on it and two 6mm screws hold it in a hole in the heater blower box.
which line are we talking about the small hard plastic line that is near the A/C freon resavour to the valve cover on the drivers side. If that's the one you'll have to take off the engine cover on the inside and it is located next to the throttle body on the drivers side. There is another soft rubber hose that comes off of that same connector near the A/C unit that goes somewere behind the alternator. I haven't found it yet been looking and searching for hours now
The heater control valve is mounted on the engine side of the heater and evaporator box which is located on the passenger side of the engine compartment. It will have at least three hoses connected to it and one vacuum line. It kind of hides underneath the a/c accumulator.