I've used conductive paint (out of a defroster grid repair kit) to repair broken traces on my 1993 Yazaki cluster with good success. If there's a broken solder joint where a component attaches to a trace, I'm not sure that conductive paint will do the job, as the part can still wiggle within the solder blob and cause an intermittent connection or a higher resistance one--the paint doesn't have the mass to immobilize the part like a large contact patch of solder would.

Reflowing the solder is a better bet, although you are right to proceed with caution doing it. And the other suggestion, about removing the screws and GENTLY cleaning all the contact areas, is spot on. After 20 years, the connections benefit from a little freshening up.

john
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1989 245 245K / 1993 945 131K