Pulsating heater blower question

SAJanesick - Bellsouth sajanesick at bellsouth.net
Wed Mar 4 06:34:49 PST 2009

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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