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My Tachometer has started acting up. It typically stays bottomed when I start the car then after 5 minutes of driving it starts to jump around then after 10 minutes of driving one solid acceleration it will start to come alive and register with correct and steady readout. Sometimes still jumping sporadically. Does this mean my instrument is starting to fail? Is this something that can be rebuilt or is my only option to just replace the instrument tach? I have attached a link to the video I took. original setup on 1982 Corvette.
The symptom described could be something loose in the wiring or one of the clips inside the housing isn't making good contact. It could also be the tach board failing.
I'd check the connection at the distributor then I'd check it at the tach filter. If nothing changes, by-pass the tach filter and see if the problem still exist.
If it goes away, replace the tach filter. If it's still there then I'd go inside the housing and check to make sure the clips are making good contact with the studs on the back of the tach and I'd probably pull the housing to make sure the fingers on the pcb behind the housing are making good contact with the connector. (instructions to remove the housing are posted below).
Jumping Tach
