Check the solder points and all electrical contacts going to the cluster.
As Rustam mentioned the contact cleaner is called Stabilant 22. It is VERY expensive these days. I still have some left that I bought from a member here a million years ago. Works very good in a dropper bottle.
For most of the electronics that I work on I use Deoxit D5 in a spray can which is a cleaner and lubricant. Used mainly in component repair such as slides, dials and switches. It is expensive but in my case it has paid for itself many times over on the first use.
95 E34 530I V2.37
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Those who make peaceful revolution impossible will make violent revolution inevitable.
John F. Kennedy