500SL instrument cluster blinking
 

I just bought a '91 500sl, It seems that when I use the turn signal lever, all the indicator lights on the instrument cluster will blink on/off momentarily, it is not left or right turn related and it does not seem to interfere with the vehicle operation, it happens only occasionally. any idea what the problem is and how to fix. thanks mike. Bmediany@aol.com

My initial guess would be a ground problem with your turn signal switch, relay, or bulbs. The "light-out" indicator on your dash would tell you if a bulb is bad (which you haven't mentioned being on), so I would surmise it's either a problem with the stalk, or the flasher relay.

Does the blinking occur when you fire up the hazards too? If not, then I would think it's the turn signal stalk...

G-Benz,

My car does same thing, both when signals are used and when harzards are turnes on.

Are you saying that if it happens when you turn on hazards, it is a flasher issue?

I assumed that flashing dash was a instrument panel issue.

MG

Check the other illuminated components throughout the cockpit as well...

...do the window and door switches, console switches and backlit climate control buttons flicker in the same manner?

I would still venture that the flasher relay has some trouble with ground.

In a related situation (on my W124), I had a ground problem with one of the terminals that housed a brake light bulb...whenever I depressed the brake pedal (at night), all of the illuminated cockpit functions would flicker rapidly!

Guys:

On the early 140, 91 models, the cluster are the analogue version rather than the digital display.

The VDO analogue cluster ised on 91 140 were having problems with the mother board requiring replacement. A Mercedes bullitten can be found on this. In the early days, MB offers just the board for dale. However now they offer the entire cluster only. The problem is the exact description, lights flushes like chrismas trees....

Search the site for 140 cluster and you will read. Its a well known problem. A bullitten can be found if you look hard enough.

Considering the similarities on the SL cluster with the S-Class, I won't be surprise the same problem exist on the 91 SL class too.

I know someone in the states offer re-built of your mother board. However for a proce of something like 500 USD. Someone tried it, and it was fixed. look in the board and u will see.

I am having the same problem with my 1992 300SD. In addition to the instrument cluster lights flashing periodically when using the turn signal they also flash when using the windshield wipers. The frequency of occurrences is highest when the wipers are set on "Intermittent." They flash approximately every 26-30 seconds during light rain, when my wipers are set on Intermittent. Much less frequently when the wipers are set on Normal or Fast. After the cluster of lights flash, the seatbealt warning light flashes four times.

Anyone with ideas? The dealer hasn't been able to replicate the problem, but it happens every day when I am driving.

Hi
My car had the same problem relating to the signal switch. All the warning lights would blink constantly. I replaced fuse 9 with the newer tube fuses and it fixed the problem right away.

sorry but what is "newer tube fuses "/??

It sounds like the instrument cluster circuit board is bad. There is an old service bulletin about this problem, but the circuit board is no longer available from MB. In addition to the cluster/warning lights flashing the guage needles would also jump erratically. There may be an after-market fix for this, but I'm not aware of one. It's ashame, because the replacement cluster isn't cheap.

Instrumnet Cluster Blinking Problem
 

How might I locate old MB Service Bulletins that address the problem with the instrumnet cluster mother board? Also, does anyone have info on potential sources for a replacement mother board since MB may no longer manufacture?

My cluster warning lights on my '91 SL would flash and my gauges reset when I used the turn signal. I did some experimenting and concluded there was a problem with voltage regulation on the cluster circuit board. A friend who is a cicuit designer suggested that there may be a large electrolytic capacitor in the power supply that had dried-out. I took the cluster out, removed the back cover, removed the main board from within the back cover, and then examined the components. There was one large electolytic on the board, and sure enough, it was in the power supply circuit. The cap is rated 470uF, but when I removed it and measured its value with my meter, it read just .2nF It's value had diminished by more than 99%.

I replaced the bad cap with a new 470uF from Radio Shack. Part number is 272-1030. No more flashing or cluster reset when I use the turn signals now.

man.... u have a photo or something? it will be nice to fix this but have no idea where on the board you are referring

Here is a picture of the capacitor. You really can't miss it. Only one other component (another cap) looks anything at all like it, and that one is significantly smaller and not 470uF. Remember, it is on the board screwed to the back cover. You must seperate the board from the cover, because you need to access both sides of the board, naturally.

just wondering could this be an easy job for non soldering expert?

Can I just cut off the old wires attached to the board and solder the new one on those wire? Does it matter if we solder in the wrong direction? i.e. left to right or right to left?

Thanks

Shek, how about emailing me if you need help with the soldering. It is not difficult, but a detail which was unique in my experience is that there are traces on both sides of the circuit board; and the capacitor looks as if it needs to be soldered on both sides. That is, one lead from the cap solders to a trace on one side and the other lead solders to a trace on the other side.

Additional note: these electrolytic caps have a "+" and "-" terminal. The "-" terminal is marked, the other is not. Observe the polarity of the old cap before you remove it and be sure to match polarity with the replacement.