Rpm gauge
3 Answers
Really nothing serviceable on the inside by the owner, except maybe the bulbs. Just getting to the bulbs requires a bucket of screws be replaced after most of the drivers side dash comes out. You can unplug cluster and check for a signal. But a lot of work from that end.
You might have a loose connection or a bad sensor. Go to an auto-parts supply and have them run a scan on the system and maybe it will find something