Bouncing Tach Syndrome

[Knightspirit]

Anyone else ever see this? Just wondering what the fix might be - is this an electrical or mechanical issue? It's been happening for a while and getting progressively worse. It used to start that way and then settle back to normal once the truck got warmed up. Not settling now though...

 

[WaltNYC]

tachometer is fed from a single wire off the alternator. The one with the 'push on' female blade end.

 

[p m]

Usually it is a sign of the alternator brushes getting worn out.(or some other alternator issue). Very rarely the tachometer itself goes bad.
I posted a write-up on an alternator rebuild on NAS-ROW.

 

[discostew]

Why would you want to fix that? Its bad ass.

 

[FatMcNasty]

I had an issue with the spade adapter bolted to the lug on mine. it had a micro crack in the metal under the plastic (the adapter). It would be good until it got warm then stop working/bouncing.

 

[Knightspirit]

tachometer is fed from a single wire off the alternator. The one with the 'push on' female blade end.

Perfect - thanks - sprayed some contact cleaner on it, we'll see what it does!