Electrical Advice Needed
There are multiple problems with these clusters, you should take the time to pull it out and go through it
In no order:
The PC board connector pins can get loose/ corroded from the PC board traces, you must solder them (or buy a Repop PC board)
The contact fingers for the IVR (gauge limiter) lose contact with the PC board you must solder jumpers across
The IVR itself should be replaced with a solid state one
The gauge studs/ nuts corrode/ get loose. Loosen/ tighten them a few times to scrub the contacts clean
While you are in there, take an erasor and buff clean the copper PC board where the dash lamp sockets go. Bend / clean the socket contacts and clean the sockets and replace the bulbs
Add a ground (I guess you did) to the cluster, but make sure it is actually a ground
This thread has been around a while it is tremendous
Printed circuit pins repair