Most modern PCB's have "plated through" holes; it isn't required to solder on both sides, the solder will wick through. The only exceptions to this is if (a). the plated through hole was damaged when the component was removed; or (b). a break in the PCB in this area caused a problem in the first place.

BTW, polarity on the capacitor is absolutely crucial. If the polarity isn't marked on the PCB, you need to note it before removal from the old cap. Some capacitors are marked with the "-" and not the "+". Many, but not all electrolytic capacitors (new ones, of course) have the + lead noticeably longer.

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86 560SL
With homebrew first gear start!
85 380SL
Daily Driver Project

http://juliepalooza.8m.com/sl/mercedes.htm

Are there any shops that can perform this repair in the Southeast or east of the Mississippi? I am not mechanically inclined, unfortunately.

I would really like to get this problem corrected without replacing the entire board. What MB dealers charge to replace this board is obcene.

You don't have to be mechanically inclined to make this repair, as it is simple to do yourself SD. Still, if you want to pay someone to do it for you, my friend Bill will for $100 if you mail him the cluster. While he is at it he will inspect the border and touch-up any dubious solder joints. Email me if interested.

to solve it by running an extra ground to the instrument cluster and then grounded it to the frame.

The gages stopped going haywire when I used the turn signal and they all returned to normal operation.

I ran a ground wire from the metal case on the instrument cluster to the inside dash. Worked great.