AC blows from Defrost and Floor on Bi-Level setting on the HVAC controller

Asked by Alvin Jul 15, 2024 at 04:04 AM about the 1992 Buick Riviera Coupe FWD

Question type: Maintenance & Repair

I have a 1992 Buick Riviera. When I purchased the car the AC wasn't
working so I never used the HVAC. I took it to the mechanic and he replaced
all the vacuum lines under the hood, converted the AC to r134 and replaced
a few other things. Well now that I have the car back the HVAC only bows
out the defrost and Floor vents but will not blow out the dash vents. Just
need a starting point of where to get this fixed. Thank you in advance.

2 Answers
310,545

Gene answered 5 months ago

This old it can be almost anything inside the dash, cracked vacuum lines, vacuum servos inoperative, stuck blend doors, control head leaking or just worn out. Now you need to go further with diagnostics.

Mark helpful
157,825

James answered 5 months ago

Sounds like he didn't hook up the main vacuum line for the system. When the system loses vacuum it defaults to defrost for safety reasons. Look for a vacuum hose coming out of the firewall. It'll probably be just hanging or broken. It should be hooked up to the intake manifold. Jim

Mark helpful

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