Tachometer

[kevin_z]

1995 Crusaders 454xl with MSTS. What drives the tach?? My port tach would hit 2800rpm, then drop to 1000. Engine still running good. I swapped tachs and the problem seemed fixed. Went out this week-end and port tach now hits 3200rpm and flutters a little bit, which causes synchronizer gauge to get off center. I checked all wires behind the helm gauge cluster. So, my next step is to check what??

 

[makomark]

Guess that means the gear went back in....congrats on that!!

The tach is driven by the waveform on the primary side of the coil....MSTS only controls when it happens. If the engine is running steady then its one of two issues: 1) tach has failed (hard or soft) or 2) wiring between coil and tach is flawed.

A common issue with the tach is the selector switch gets corroded and induces false output values....sometimes a good spray with WD-40 and multiple rotations of the switch will resolve it - for the short term....on the wiring side, the main harness pins come to mind....and any other connectors behind the helm....

 

[kevin_z]

Yes, the new v-drive went in. Sorry I didn't report on that. Was a very easy job actually. And that's the same side I'm having tach issues. I will look at the harness and the pins and then will disassemble the helm again and take a re-look at the wiring back there once the rain stops