Weird A/C behavior

Doyt W. Echelberger Doyt at
Sun Aug 18 11:57:27 EDT 2002

Hello Paul......I just got home from a long trip and have some additional
peculiar A/C behavior to report.

Bentley indicates that the dash vents are programmed to be closed on
AUTO-HIGH explains why they don't blow when I expect them to.  I'm going to
keep the fan speed setting on LOW when I use AUTO, and see if the center
vents come on any sooner.

There is a discrepancy between what the system is designed to do according
to Bentley, and what it does in my 15 year old car.

On my trip, I had the system set at AUTO-HIGH, and after about an hour of
driving it was blowing cold air through the dash vents. And that isn't
suppose to happen.  When I shut the engine down at a rest stop and
restarted it, the dash vents stayed closed at the same setting for another
hour, and then opened up....although not all the way. It was like it was
set on BI-LEVEL.

Getting to a solution.....Eric Kissel reports that he placed a zip tie to
keep the dash vents open. (I'm uninformed about where all these flaps are
located and accessed.)

My 86-88 5k Bentley shows a diagram at 87.128  and another at 87.174  and

I'm considering the zip tie solution, and I am wondering if I should be
reclining upside down under the dash in the passenger front, or peering
down into the air conditioner bay from the outside of the car, with the
plastic rain shield cover off, to do the zip tie trick. Need some basic

Thought you might be interested in how this is developing.

Doyt Echelberger
87 5ktq in Ohio   USA

At 08:26 AM 8/16/2002 -0400, Kneale wrote:
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.

At 07:16 AM 08/16/2002 -0400, Doyt W. Echelberger wrote:

When I took a few hours to clean out the leaves (by opening the under-dash
hinged door behind the glove box) I found the hose to the vacuum solenoid
disconnected and dangling, and the solenoid was loose in it's plastic
support cage. I used epoxy to attach the solenoid to it's cage and to hold
the hose to the solenoid. This fix didn't change anything in the way it
worked, so I'm going to go back under with a flashlight and see if I have
any new insights while upside down, curled up like a pretzel. And I'll try
the "Econ" and letting up on the throttle trick. Be assured, you will all
hear of any success.

Let's stay with this until we get it working right.  Thankfully, the
default position does cool the cabin fairly well on my car, most of the time.

Doyt Echelberger
87 5ktq in hot and humid Ohio

At 05:09 AM 8/16/2002 -0400, Larry Leung wrote:
Paul, Doyt,

I have a combination of your problems. I have the ability to get cooled
air through the dash vents,
but after awhile it blows out the defroster and floor (though not too
strongly). I have found two things
restore things to the dash (basically Paul's trick, turn the CC to ECON,
back off the throttle (raise the
vacuum), air out the dash vents again, turn back to A/C), or raise the
set temperature to the point the
fan doesn't run at full speed. I BELIEVE that it's a vacuum problem,
however I have yet to trace all the
leaks in the car's system (i.e. I don't quite pass the dipstick test) so
I'm not sure. Perhaps it's a leaking
servo under the dash. The problem is it's WAY too hot to work on the car,
especially under the dash
under the greenhouse in the hot sun. Ugh. Anyone have any other ideas?

LL - NY       l.leung at


 > Date: Thu, 15 Aug 2002 22:38:31 -0400
 > To: "Paul R. Luevano" <paul at>
 > From: "Doyt W. Echelberger" <Doyt at>
 > Subject: Re: Weird AC Behavior
 > Cc: quattro at
 > Paul, it does my heart good to read your story.  The A/C of my 87
 > 5ktq has
 > been doing that with increasing frequency for the past two years.
 > This
 > summer it has gotten to where it almost never blows out the dash
 > vents when
 > set on "Auto."
 > Check out Scott's stuff at the address below and let me know if you
 > can
 > make yours work.

 >Doyt at>

 >  >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
 > At 08:45 PM 8/15/2002 -0400, Paul wrote wrote:
 > >OK, so it has been hot .............snip...............
 > >
 > >Over the last few days, I have observed a very weird occurrence.
 > When set to
 > >"Auto" the AC will stop blowing from the dash vents.  This can
 > happen after
 > >several minutes or after just a few seconds.  It seems to blow out
 > of the
 > >defrost vents, but very weakly. Here is the weird part, if I switch
 > it to
 > >"Econ", it blows out of the dash vents with a vengeance.  I can
 > then
 > >switch back
 > >to "Auto" and it will repeat, lasting from several seconds to
 > several minutes.
 >                       paul at

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