Weird A/C behavior

Mike Veglia msvphoto at
Fri Aug 16 11:20:28 EDT 2002

In a message dated 8/16/2002 Kneale Brownson  writes:

<< That vacuum servo in the evaporator box only adjusts the amount of air
going into the HVAC system from either outside or inside the cabin.  I
suppose if the vacuum leaked there, it could reduce vacuum available to run
the other parts of the system.  But if the servo is just moving itself
because it's detached, I wouldn't think it would have any effect on which
course the air took subsequently in the system.  That's managed by the
heater core box flap controls and the servo motors under the dash behind
the radio, I think. >>

Any vacuum leak in any part of the climate control system will result in not
enough available vacuum in the reservoir to pull in the vent flaps. Dealing
with the recirculation flaps, as Doyt has done, is a critical first step. He
mentioned the hose was adrift. That's fix number one. IME, it was not just
one thing that got the climate control working well again. Next step, pull
the programmer and resolder it. Given the heat cycling they get (both from
components on the board and from huge ambient temp swings under the dash)
I'm sure that virtually all need some resoldering by now.

Don't overlook the check valve either. If it is no longer checking vacuum
from the reservoir, then vacuum can leak back into the intake tract. (See if
it holds vacuum when vacuum is pulled from the inlet side.)

HTH and keep pluggin' away at it.

Of course I'm jealous--I would much rather be troubleshooting this on my car
rather than having to change the compressor, etc. and recharging it. (And
being dark blue it needs AC--bad.)

Mike Veglia
Motor Sport Visions Photography

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