Pulsating heater blower question

[Ed Kellock]

First of all, your "AWD" is always engaged.  ;-)  Quattro is full-time all
wheel drive, always engaged.  It is only when there are some slippery
conditions that the center differential will do some real work and
reapportion torque.

In regard to your blower question, I believe you are right with your more
practical suggestion of worn brushes and the One of the cadre of
mechanically inclined friends seems to be typically grasping at expensive,
paranoid straws.  I wonder if the local garage sees few foreign cars, as
that sort of diagnosis seems to come from a cynical fear of anything
foreign.  Just joshing for the most part though. 

With 223k, I think you've gotten much more out of the blower motor than most
do.  How long have you owned the car?  It may have been replaced before, but
not necessarily.  I have nursed old blower motors along by doing a couple of
different things because replacing it is not fun or cheap, depending on if
you do it yourself or not.  The part is not especially pricey.

One thing to do is clean the brushes.  You can do this by lifting the
underhood cowling at the firewall edge and going under it from the driver's
side.  There's a small 90-degree bit of hose on the blower housing that
directs air on the brushes to cool them.  If you pull the end of the hose
that is closer to you out of the blower housing you can actually see one of
the brushes.  I have used electrical parts cleaner spray and WD40,
alternating a couple times between the two, to clean and lubricate the area.
Sometimes this has been all I needed to do.  It really is just putting off
the inevitable however.  And, depending on the condition in there, I suppose
it's possible that you might wash away the last bits of anything that are
making contact.  So just be prepared that you might make it worse.  This has
not been my experience, but I feel it's worth mentioning in case you have an
impending need for a functioning system for a trip or something.  

Anyway, I've kept blower's going on a couple of my cars doing that.

The brush is in a little cage or tower that has a spring that pushes it
against the spinning electrical rotor in there.  Some people have also
gained some time by using the eraser end of a pencil to push down on the
tower or spring to make it tighter, to cause the brush to be pushed a little
bit harder on the rotor.  You can't access the other brush in there, but
this slight "snugging" seems to help in some cases. 

If you're game and prepared to possible have no blowing action, I think I'd
suggest the spray cleaner approach first.

Ed

-----Original Message-----
From: 200q20v-bounces at audifans.com [mailto:200q20v-bounces at audifans.com] On
Behalf Of SAJanesick - Bellsouth
Sent: Wednesday, March 04, 2009 7:35 AM
To: 200q20v at audifans.com
Subject: Pulsating heater blower question


The problem car: 1991 200 20V TQ - 3B - stock except the IA III+ chipped ECU
and 034 silicon intake hoses

Unlike you hearty folk living up north (except on occasions like Monday -
first measurable snowfall here in about a half dozen years), my AWD is
rarely engaged save the occasional quick start in the rain.  However, I
actually do use my heater/defroster regularly in spite of our more moderate
temperatures here below the Mason-Dixon line.  The problem is after 223K
miles, it seems my heating and A/C blower is protesting.

The blower is working, just intermittently.  Usually in the cooler months, I
punch the econ switch and then vary air flow and temperature manually.  A
few weeks ago I first noticed the problem only when making a right hand
turns.  Although the blower would seem to be operating while I was driving
in a straight line, even the slightest turn to the right would result in a
blast of air from the blower as if it were momentarily put on high.  Soon as
I straightened out, the blower speed would go back to normal where it would
stay until my next right turn.

The turns could be either something modest like entering an intersection and
turning to the right, or something more energetic like taking a sweeper on a
twisty back road.  However, sensitivity eventually increased to the point
where I can simply be maneuvering in a parking lot and that will be enough
to engage the blower motor speed change.  Also at some point, depending upon
how level the cars is, the blower will occasionally pulsate while the car is
stopped, sometime pretty rapidly - perhaps on 1 second cycles - between high
and low until the car is moved.  Finally the symptom also started to occur
while turning to the left.

I have done nothing yet in terms of diagnosing the problem other than
demonstrating it to a cadre of mechanically inclined friends at a local
garage.  One guy thought it was the head unit to he climate control, I think
it might be a physical wearing of the blower motor brushes that have lost
contact other than when pushed to the right or left through the efforts of
G-forces, and another guy could neither hear nor understand the problem
(we're all getting old and deaf).

Mostly I'm just looking for either someone who has experienced like problem
and can point me to a link or posting that deals with it, or someone who can
at least confirm the identical problem and give me a rough outline as the to
cure, or any other thoughts or ideas from enlightened individuals familiar
with the territory.

Last but not lest, I have not yet worked my through the 82 pages of
Bentley's VOL 2 section "D" diagnostics (O.K., 80 pages if you don't count
the intentional blanks), thinking someone out there might save me a little
time, but I'm not opposed to it if no one out there has anything to add.   

All help appreciated.  Until the weather warms up, guess I'll just keep
trying to find the twisty way home.


            - Steve Janesick
              Oak Ridge, NC
              sajanesick at bellsouth.net



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