[W126 Coupe] electrical expertise needed

Wed Oct 5 16:38:45 EDT 2005

Markus,

I think organizing a get-together is a great idea.

Speaking of creating more problems than you are solving; here is my sad list
of accomplishments with the instrument cluster:

I first started out with a stock instrument cluster with all parts working
properly, except the clock. As I was going to remove the instrument cluster,
I thought I'd do some "upgrades" while I was at it so I bought White Face
Gauges off of ebay for $25, capacitors at Radio Shack for $2.50, red paint
and black paint (for instrument needles) for $5 at Wal-Mart, Chrome Rings
for the instrument binnacle for $60 and Wood Surround for the dials for $120
from mercedesperformance.co.uk.

Well, the burled walnut wood surround is impossible to install unless you
separate the front glass from the black plastic binnacle and those parts are
very well glued together. I broke the damn $120 part in the process of
trying to insert it through the openings in the back.

Next; fix the clock. Not very successful, as you can tell.

Install white face dials. Broke the fuel gauge needle, put the oil pressure
needle on while the paint was still wet an glued it to the pin it rests on,
put the temp gauge needle on wrong making it show 20 degrees more than it
should (giving me a heart attack as I thought the engine was overheating).
Had to buy a new fuel/oil pressure/economy/water temp gauge off ebay for $20
to replace the one I wrecked.

Chrome rings, a PITA to install as you have to insert them through the
binnacle and then press them in place. There is no going back because the
glue they come delivered with is sticky mess and impossible to remove.

..and my clock still does not work (I'm really getting good at removing and
installing the instrument cluster though.).

Cheers,

Axel

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Markus Meyer
Sent: Wednesday, October 05, 2005 3:43 PM
To: mbcoupes at mbcoupes.com
Subject: RE: [W126 Coupe] electrical expertise needed

Axel,

Check out Chet's writeup. If you need it, let me know, I have the email
saved off. I believe he said the capacitor is the same as in the two
configuration. Funny thing is, it doesn't look like my capacitors were
replaced, or if they did, they found ones looking just like the stock ones.
I bought the ones from Radio Shack, and they were a lot thinner than the
stock ones on my clock, maybe other manufacturers make them looking more
like stock. Anyhow, it is exactly what you state (replacing them and it
still not working) as well as having an issue when I tried fixing one to
begin with and causing more problems that I decided to let someone else do
it. Didn't want to spend the money if $2 worth of parts would have cured it,
but when I caused more grief than fixing I gave up and decided my electrical
skills weren't going to be practiced on the SEC anymore.

BTW, how's your car? We should get together, living so close. Actually, the
Del Valley "group" should speak up and let us know if sometime next month is
good to get together, it's been a while!

Cheers,
Markus

--- On Wed 10/05, Axel Wulff < axelwulff at hotmail.com > wrote:

From: Axel Wulff [mailto: axelwulff at hotmail.com]
To: mfmeyer at iwon.com, mbcoupes at mbcoupes.com
Date: Wed, 5 Oct 2005 13:58:05 -0400
Subject: RE: [W126 Coupe] electrical expertise needed

Hi Markus,

I have the same issue with the clock in my 90 SEC. It works intermittently
and has only one capacitor.

I got hold of a write-up on fixing the two-capacitor clock, which needs two
100uF 35V DC (Radio Shack part number 272-1028) capacitors.

When I removed the old capacitor from my clock, I could not find any
identification on the part, nor its technical data, so I tried the 100uF
capacitor which did not solve the problem.

Does anyone know if the capacitor is different in the one-capacitor clock
from the two-capacitor model?

I may have other problems than the capacitor.

P.S. My instrument cluster has an electronic dimmer unit, not the mechanical
one with a coil.

Cheers,

Axel

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Markus Meyer
Sent: Wednesday, October 05, 2005 11:44 AM
To: figstir at yahoo.com
Cc: mbcoupes at mbcoupes.com
Subject: Re: [W126 Coupe] electrical expertise needed

An update on my intermittent working clock issue. I took the clock out and
attached it to a free standing 12 volt battery from my alarm system, as well
as the car battery. Didn't change a thing. Everything else checked out okay,
so I UPSed it off to The Benz Store, and a few days later I got a box back
with a unit that I plugged in, and since Monday night, has been working
non-stop. Not sure what they changed or fixed or updated, but all I know is
I have a non-intermittent working clock again (knock on wood!). Thanks to
Dick for the suggestion on using them. Chet - if you are out there, I still
have a spare I picked up on ebay from an 89, and you are correct, it only
has 1 capacitor as opposed to my 87 with 2. Anyhow, next time we get
together maybe you can show me how to swap the capacitor on that unit to see
if it will also start working regularly again.

Thanks to all who offered help and suggestions.
Markus

--- On Wed 09/14, a figment of the imagination < figstir at yahoo.com > wrote:

From: a figment of the imagination [mailto: figstir at yahoo.com]
To: mfmeyer at iwon.com
Date: Wed, 14 Sep 2005 09:31:58 -0700 (PDT)
Subject: Re: [W126 Coupe] electrical expertise needed

Hey Markus,

It sounds like a voltage problem right off the bat.

Dick's suggestions can be confirmed by myself, as
well.

I would like to add the following.

1. The terminal off the back of the instrument cluster
behind the tach is attached to a reddish wire which
provides 12-volts. Test this wire to make sure you
are getting the proper voltage; it should be around 12
volts, although the clock should probably be able to
work with as low as 9-volts. 

2. If the voltage is low, then you have other obvious
issues, with regards to the battery, alternator, or
other.

3. With the clock and/or instrument cluster off the
car, simply connect 12-volts directly to this same
lead from a separate 12-volt source. Use the negative
terminal as your ground; you should be able to find
the common terminal to the clock easily on the clock
itself or on the back of the instrument cluster. I am
sure that this is what you were thinking and were
asking about.

My only concern here is that you make sure you are
connecting directly to the clock. There are indeed
capacitors, IC chips, transistors, and resistors in
the back of the instrument cluster that could be
damaged, by accident, if the are connected to 12-volts
directly when they were not designed to be. The
terminal mentioned in #1 should be fine but check it
just in case.

4. Your ground on your instrument cluster could be
faulty. While for me the jury is still out, I am
aware of others with SEC's having problems with faulty
grounding on their instrument cluster. I currently
have possibly a faulty ground to my instrument lights,
causing them to fail. My comment about a faulty
ground is that, if this was indeed the problem, then
you should see other problems with other electronics. 

5. Based on this logic in #4, which may not be fully
complete, I would suggest that you may not have the
proper voltage being sent to the clock. As stated in
#1, check it. Check the battery level, check the
alternator, check for other problems with other
devices or shorts. 

6. In general, a faulty capacitor should have nothing
to do with intermittent operation of your clock. A
capacitor merely stores a set amount of voltage, after
being in properly adjusted with resistors and other
elements. You seem to be describing a run-down type
of phenomenon, kinda like a "subclavian steal" in
medicine or even "sun-downing" in psych, or some
better analogy. [Hence, alternator, battery, etc..
issues]. I highly doubt a faulty capacitor would allow
for intermittent operation, but a faulty and
non-constant voltage supply would.

I'm sure your clock is good! You may need to take
care of a loose connection somewhere. You can check
continuity and resolder broken or faulty leads or
terminals. Make sure you check voltage, as I
mentioned in #1. Another analogy is your analog clock
in your home/work, which slowly runs down or stops
working as the AA battery dies off. If you are
draining the battery as you go throughout the day,
your clock will be affected. If this is indeed the
cause, how this drain is occuring needs to be
investigated.

7. Regarding a good direct grounding point, I
recommend the common ground source behind the
instrument cluster. There are at least 3 big bolts
holding down the terminals of numerous brown leads.

If this is helpful, that's great. If not, keep trying
with these and others' suggestions. I am certain it
is very simple. Please keep me informed.

Cheers!

-fig

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