Mercedes instrument cluster issue W140/R129

Yea,I checked my fuses in the engine bay by the fender all are good.I even had them all replaced about a year ago..I detected that my battery kept draining overnite for no obvious reason.After weeks of sleepless nights and a million test.I finally traced my battery drain issue to the back of my alternator.There are two wiring harness stems on the back of alternator.One screws on harness that comes from the battery in the trunk and the other goes to the car's electronics/computer including the instrument cluster.Without proper contact one the small wire/stem my alternator was not getting good ground..This caused it to have the drain overnite.It was only when I decided to take the alternator out to get replaced did I notice that the contact on the back of the alternator was not sitting flush.This is the little stem that the smaller wiring harness hooks up too..The nut that holds the actual stem from the alternator was not tight enough.That fixed my issue after getting a new alternator since I had a lifetime replacement.I just sent off my cluster to a repair center in Massachusetts today.I will keep you guys posted on what parts were changed or repaired.Hopefully that will help shed some more light on our cluster issues.
Thx.

Well folks,I needed to update everyone on my findings.My R129 cluster as I stated was sent for repair.I got a call from the repair center that apparently my circuit board was damaged and beyond repair.The service center had another cluster which they sold me.I was glad to get another cluster but soon realized another issue.The cluster that the service center sold me had two issues 1) Erratic or jumpy speedometer and fuel gauge reading was wrong by about 1/4 tank more? I immediately suspected that this was probably for a W140 body or needed calibration? I sent it back to the service center and they checked it and found no faults.I even opened up the unit and found a R129 sticker on the circuit board but not sure why my speedometer was jumpy and wrong fuel reading.This actually caused me to run out of gas one night just 3 blocks from home..You can guess how frustrating I was! I then decided to either bite the bullet and order a new one from the dealer for $998 or try to find another used one online.I took the chance and picked up one online which now works perfectly.So to summarize the issue, my original cluster could have been repaired by just changing the three capacitors on the circuit board.If that does not fix your issue,then you most likely have a damaged circuit board like mine which may not be repairable.Hope this info helps someone.Good luck.Thanks to all the members that contributed to this thread.