how can i test my tach?

[lonesouth]

the tach on my boat doesn't work. How can i test it to see if it is the tach or the signal? I'm fairly electronics savy, but have never worked with a tach.

thanks

 

[jhebert]

Re: how can i test my tach?

If an outboard motor tachometer:

To test the tachometer signal, connect an oscilloscope to it. You should see a pulsing DC waveform with a positive peak near the battery voltage, a negative peak near ground or slightly below, and a frequency that corresponds to the rotational speed of the engine multiplied by the number of pulses used in the tachometer calibration setting. For example, if a six-pulse tachometer and the engine running at 600-RPM, the frequency of the tachometer signal would be

600-Revolutions/Min x 6-pulses/1-revolution x 1-min/60-sec = 60-pulses/sec

 

[Barnacle_Bill]

Re: how can i test my tach?

Take it out and find a shop that has a tester. I know our local BPS has one but don't know if all of them do or not.

 

[lonesouth]

Re: how can i test my tach?

sorry, should have been more concise. it is a Faria tach for an Johnson V4.

sounds like i should be able to use a DMM to check frequency? don't have an o-scope...