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Gary, Chevy Technician
Category: Chevy
Satisfied Customers: 17143
Experience:  15 years GM master tech
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1999 Chevy Astro: replacing HVAC vacum line which controls air flow

Resolved Question:

I have a 1999 Chevy Astro I was wondering if you could help me with replacing HVAC vacum line which controls air flow.
Submitted: 6 years ago.
Category: Chevy
Expert:  Gary replied 6 years ago.
so you do not have vacuum coming inside the truck and you have no mode control for the heater a/c system?
Customer: replied 6 years ago.
All switches everything in tack, when I turn on AC it will blow cold for awhile and then get warmer
Expert:  Gary replied 6 years ago.
will the heater a/c change from defrost and floor no problem?
Customer: replied 6 years ago.

When accelerating upgrade output dies off

Expert:  Gary replied 6 years ago.
graphicgraphicok open the hood and find this vacuum reservoir here in this picture.once you have found it with the engine running pop off the vacuum line going to it and see if you feel good vacuum.if not follow that line up it should hit a T off of another vacuum line.follow the BOT lines one goes to the engine and make sure the plastic line is not cracked or chewed threw or looks rotten.that vacuum reservoir should hold a reserve of vacuum to STOP you loosing vacuum going up hills.i think you will find a bad vacuum line off the engine to that T or the line from the T to that reservoir.if those lines are 100% perfect NO leaks you might want to look and see if that plastic reservoir is cracked or damaged
Customer: replied 6 years ago.
Should I remove aircleaner or any other accessories to expose these lines. Can you forward me a better diagram so I can clearly see the parts you are talking about on the engine
Expert:  Gary replied 6 years ago.
that vaccum tank is located standing at the front of the van to your left just below the heater box attached to the inner fenderwell.using this picture( the best one i have of the area)between this picture and the other picture i sent you its located under the area of # XXXXX shouldnt have to remove the the engine cover at all.maybe the aircleaner to get a better viewgraphic
Customer: replied 6 years ago.

Should I be concerned with the heater control valve.

Expert:  Gary replied 6 years ago.
what do you mean?
Customer: replied 6 years ago.
Would this have anything to do with the vacum line operation?
Expert:  Gary replied 6 years ago.
hard to tell that vacuum has to be fixed first.the temp doors are controlled by an electric actuator.but first fix that vacuum problem.then see how it works
Customer: replied 6 years ago.

Will the heater control valve be in my way to access any of the vacum lines?

Expert:  Gary replied 6 years ago.
no.any vacuum problems you are having are all under the hood and fixed by the way i told you to approach the problem
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