[R129 SL] Center vent issue resolved

Fri Oct 21 17:00:44 EDT 2005

Original problem was posed last year.  Finally repaired a year later when my
ACC controller went bad.
Scroll down for final answer:

On 8/28/04 8:22 PM, "Deneal Schilmeister (iMac)" <deneals at mbz.org
<http://striplin.net/mailman/listinfo/mercedes_striplin.net> > wrote:

> In the last two days, I've noticed a very peculiar smell in my SL500. I'm
> posting about it in case anyone might be familiar with this, although I
know
> its IMPOSSIBLE to describe this smell.
> 
> It's hard to describe because it is a smell I've never encountered, nor
near
> anything I can describe.
> 
> It seems to originate from the ventilation system, although I can't be
sure
> yet.
> 
> The smell is like a plastic burning smell, without the burning part.  Very
> close to the plastic burning insulation smell of an electrical problem,
> without the "acridity" of the electric burning part of the smell.
> 
> Well, that's the best I can describe it.  I'll take it to my indie guy on
> Monday, but I thought I would present it here to see if anyone can add
some
> help.
> 
> Thanks alot

On 8/30/04 8:50 AM, "Marshall Booth" <mbooth+ at pitt.edu
<http://striplin.net/mailman/listinfo/mercedes_striplin.net> > wrote:

> A smell similar to what you describe accompanied the demise of the
> windshield washer nozzle heaters on my 201 series cars. It appeared and
> lasted several day on the two 201 I own that had windshild washer
> heaters. The smell was gone a few days later and the washer nozzle
> heaters have not worked since then.
> 
> Marshall 
> -- 
>  Marshall Booth (who doesn't respond to unsigned questions)
>     "der Dieseling Doktor" mbooth at pitt.edu
<http://striplin.net/mailman/listinfo/mercedes_striplin.net> 
> '87 300TD 180Kmi,'87 190D 2.5 198Kmi, '84 190D 2.2 227Kmi, '85 190D 2.0
> 159Kmi, '87 190D 2.5 turbo 231kmi
>     Diesel Technical Advisor MBCA, member GWSection
>   http://www.dhc.net/~pmhack/mercedes/mbooth1.htm
<http://www.dhc.net/%7Epmhack/mercedes/mbooth1.htm> 

THE FINAL ANSWER

The R129 roadster, as part of the center vent system, has an electronic
circuit board in the bottom of the vents that controls the opening and
closing of the dashboard vents, operated through rheostat type switches
located at the lower portion of the center vents.

In warm weather, should one be driving with the top down and the air
conditioning on, condensation builds up on the center vents, which then
drips down into the unit and onto the PC board. The center vent unit
connects via pin connectors on the bottom of the unit.

This dripping eventually shorts out the board and/or the connector pins,
which then wreak havoc with the ACC unit.

Although my indie has always talked about the expense to replace this unit;
(indicating to me the repair community is aware of a problem) neither he nor
the dealership could figure out why my ACC unit went crazy.  Replacing the
ACC unit twice did nothing.

Finally, I took the car to the dealer, who agreed to throw parts at it until
it was fixed.

First they replaced the auxiliary vacuum pump, which did not fix the
problem.  Then they replaced the center vent assembly and all worked as it
should.

They had the car for three days, and ended up charging me 8 hours for
diagnosis, $264 for the aux vacuum pump, and $580 for the center vent
assembly (they call it part# 129-830-06-9115 Nozzle)

I believe that this electronic center vent unit is unique to the R129 cars.

So the moral of the story.... If you have one of these cars, don't drive
with the top down ad the air conditioner on to the point that condensation
accumulates on the center vents!

+++++++++-- 
Deneal Schilmeister
MBCA Gateway 1991-2005
1997 SL500     (96k)
http://homepage.mac.com/deneals/SL500.htm
http://homepage.mac.com/deneals
+++++++++--

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