Erratic tachometer reading

[Robob]

I recently replaced my old dead tachometer and now it works okay up to about 4,500 RPM but above that it pegs the needle. It works okay when I back off on the throttle.

I tested the rectifier with a good ohmmeter and also the charging voltage at the battery shows 13.5 volts although the in dash voltmeter (probably inaccurate) only shows about 11.5 volts. I don't think it's the rectifier.

Any suggestions?

Thanks,

Bob on Tampa Bay

[seabob4]

Bob,
First, did you actually test the voltmeter on the terminals on the back side, or is that just what the gauge face reads?

Secondly, there is not much you can do to T/S a tach.  Make sure all terminations are tight, that you have good voltage on the ignition wire (purple).  I believe the sending wire (gray) has around 5.5V when the motor is running.

And I don't think it has anything to do with your "pole" setting, as then your readings would be erratic throughout the tachs range...

[Robob]

It's just what the dash voltage meter reads and I have read that they are very inaccurate so I tested the main battery leads with the engine off and running and am satisfied that the voltages are good.

I'll test the voltage meter terminals the same way.

I'll also have to take the tach out and make sure all my new connections stayed tight.

Thanks again,

Bob on Tampa Bay