tachometer testing

[Michael Nehra]

How can I test a tachometer that is electronic/not mechanical, when not hooked up within the dash? Is there a simple test procedure?
Thanks
Mike Nehra/member

[Mark P.]

Re: tachometer testing

My electronic timing light can be used as tachometer. It is just hooked up in the same manner as you do dwell adjustment.
Maybe your local car supply shop has something similar.

[Mark P.]

Re: tachometer testing

My electronic timing light can be used as tachometer. It is just hooked up in the same manner as you do dwell adjustment.
Maybe your local car supply shop has something similar.

[Michael Nehra]

Re: tachometer testing

Mark, I am trying to test the tach itself, outside of it's circuit in the car. Any suggestion of how to do this?
Thanks
Mike

[Michael Nehra]

Re: tachometer testing

Mark, I am trying to test the tach itself, outside of it's circuit in the car. Any suggestion of how to do this?
Thanks
Mike

[Wayne C.]

Re: tachometer testing

I don't know what tach you have, and probably wouldn't have an electrical diagram for your car even it I did, but...

I think most electronic tachometers have just two electrical leads, one for the "tach" terminal on the HEI distributor (and, hopefully, labelled "tach" on the tachometer unit itself), the other for ground. NEVER connect the tach lead on the tachometer or distributor to ground. The tach terminal on the HEI is the one to the left when looking at the distributor from the driver's side (ie, from the side of the cap the terminals are on).

If there are 3 leads, the third goes to 12v battery positive, although I guess it's possible to have a "tach" lead and a 12v positive lead, with the ground being the tachometer case.

So, you should be able to use test leads and any car with an HEI distributor to test your tach unit, being certain to connect "tach" on the tachometer to "tach" on the distributor; if the second tachometer wire isn't marked (BTW, ground wires are often black with a white trailer stripe), try connecting it to ground first... if that doesn't work, then you could probably connect a test ground lead to the metal part of the case and then connect the second tachometer wire to 12v positive.

[Wayne C.]

Re: tachometer testing

I don't know what tach you have, and probably wouldn't have an electrical diagram for your car even it I did, but...

I think most electronic tachometers have just two electrical leads, one for the "tach" terminal on the HEI distributor (and, hopefully, labelled "tach" on the tachometer unit itself), the other for ground. NEVER connect the tach lead on the tachometer or distributor to ground. The tach terminal on the HEI is the one to the left when looking at the distributor from the driver's side (ie, from the side of the cap the terminals are on).

If there are 3 leads, the third goes to 12v battery positive, although I guess it's possible to have a "tach" lead and a 12v positive lead, with the ground being the tachometer case.

So, you should be able to use test leads and any car with an HEI distributor to test your tach unit, being certain to connect "tach" on the tachometer to "tach" on the distributor; if the second tachometer wire isn't marked (BTW, ground wires are often black with a white trailer stripe), try connecting it to ground first... if that doesn't work, then you could probably connect a test ground lead to the metal part of the case and then connect the second tachometer wire to 12v positive.