1992 300SE (140) lights flashing on cluster (pls help)
 

Ok, I have a crazy issue going on with the instrument cluster. Anytime I engage the turn signal (either left or right) the guages on the instrument cluster go whacko and a bunch of warning lights come on for about a second. This only happens when I either engage the turn signal left or right.
Some techs have told me the instrument cluster has to be changed ($800) and some other techs who have seen the car have said they just don't know what it is. I am hesitant for now to change out the cluster and blow $800.

The car runs absolutely fine, only when I engage the left or right turn signal it seems the instrument cluster just goes all whacko for about 1 second like its been possessed and returns to normal

any ideas? Thanks

It is a very common issue on the pre 94/5 cars. the voltage regulator in the cluster becomes unstable. there have been some who replaced the regulator capacitor with sucess, it requires the removal and soldering on the cluster. There are others who claim it could be a bad ground, bad regulator in the alternator. It happens to trigger with the windshield wiper, turn signal, and lately when my wife turns on the mirror lamp in the visor.
Then there is MB who was swapping out clusters and selling a new "board" during and post warranty for the digital odometer version. Mercedes is selling a new cluster for $ 1,000, coded to your mileage there are some who are rebuilding them.
This company describes the symptoms and repairs clusters but in Canada
http://mbcluster.com/
This is a US location
http://www.bba-reman.com/catalogue/DetailedProduct.aspx?DetailedProduct=393

benz world members forum
http://www.benzworld.org/forums/search.php?searchid=3623239
various members input including mine

No doubt this is caused by a dried-up capacitor in the voltage regulator circuit in the cluster main board. It is easily replaced, and countless people have done the repair. This thread shows the location of the capacitor on the cluster of an R129 SL: http://www.peachparts.com/shopforum/984734-post8.html.

thanks for that info BobTerry..

Now, where can I get one of these capacitors? At a local Radio Shack or do I have to go to the dealer? Also, how much do they generally cost? I'm going to try this first before I do anything. Again, thanks for your help.

You can get a capacitor at Radio Shack. Cost will be less than $2.

I hope you have experince working with printed circuits, like a solder sucker, low wattage soldering iron, and have the dash removal tools. The Benz world link also has photos...

Ok great. Thank you all.

BobTerry: What size Capacitor do i need? volts/watts? And how many are there total to swap?

Peter: I have the pulling hooks to get the cluster out. Piece of cake, I can get the cluster out in less than 3 min.

I haven't used a soldering iron in awhile, but will pick one up at my local HomeDepot/Lowe's and atleast attempt to change these capacitors. Can't hurt, can it? :o

BobTerry: What size Capacitor do i need? volts/watts? And how many are there total to swap?


Eesh, you're making me nervous just by asking that question. Capacitors have no such thing as a wattage rating. They have 3 ratings. First is capacitance, measured in microfarads. Second is voltage, which tells you how many volts the cap will take before exploding, and finally there is temperature.

What you want for this type of circuit is a cap that is has at least as much capacitance as the original or more, and the same is true of the voltage. Don't go overboard and put a cap 100x the original value, as that might be problematic, but twice or three times the original value would be fine. This is good to know because you can't always find a cap that is the exact same value. Please keep in mind that what I am saying only applies to filter capacitors in power supplies. Other circuits may very well need to have the cap be an exact or approximate value. But if we're talking voltage regulator cap here, then you can go at least 2x original capacitance, and you absolutely SHOULD get one at a higher voltage rating than the original (it DID fail after all). Temp rating should be no lower than 80 degrees celsius, preferably 85. They just last longer.

If you haven't soldered in a while, do yourself a favor and brush up your skills on an old clock radio. Don't risk breaking a trace on your MB instrument cluster.

Also, you need to know if the cap you are replacing is axial or radial. An axial cap has one lead at each end, a radial has both leads on one end. If the cap you are replacing is radial, you will need to select a replacement that is of the same physical size with respect to the distance between the leads and their wire gauge. With some skill, you can generally get an axial to work in place of a radial, you just have to insulate the lead sticking out of the top and bend it over to the board.

MAKE SURE you mark which end of the cap is negative on the board, as electrolytic capacitors tend to explode when hooked up backwards.


If you want, I'll be happy to do it for you if you pay for the shipping.


-tp

get a small iron and rosin core solder at Radio Shack along with the capacitor The part was 450 mf at 25 volts, but 1000 to 3000 have ben used
I posted this link along with pictures
http://www.benzworld.org/forums/sear...archid=3623239

I am going to attempt this repair on my W140.

Is the circuit board subject to getting zapped by static electricity like a computer circuit board would be? How careful should I be with it?

Thanks to all posters for the great information.

Harry

Ok, so I attempted this fix today and swapped out the capacitor. Plugged back the instrument cluster in and now the fuel guage, speedometer and oil guage does not work!! :mad::mad:

Basically, the only thing that works are the turn signals. Not sure what to do now? I am thinking about using MBCluster.com and sending it to them for this fix.

The capacitor was only $1.29 at Radio Shack (470 UF at 35 volts) and the Soldering set was only $8.99.

Help :(

By no means I'm an expert but I had the same issue with my instrument cluster and was able to fix it myself.

One thing I can think of is the polarity of the capacitor. Did you note the polarity of the original cap before replacing it?

Hi Chedeng,

The original capacitor was 470uf 16V. The one I replaced it with from Radio Shack was 470uf 35v. Could this be causing the problem? Looking at them physically, the stock capacitor is slightly larger in physical size than the replacement.

I see you're in Rockland County as well -- we're neighbors :)

Thanks,
Agron

Agron,

I replaced mine using the same capacitor which was also from Radio Shack 470uf 35v so it should have worked fine. Unless something has happened while you were working on it like static electricity zapping other components then it might not be easily corrected. I will let others chime in.

I sent you a pm also.

thx
chedeng

I don't think so. But maybe Agron's board was zapped with ESD. May as well ground yourself with a bare wire wrapped around you wrist or finger.