How to bench test 71 Cuda rally dash tachometer

[DocMel]

My original tach is shot:  I have a OEM/used replacement not currently installed

How can I bench test it to see if it works?  Be advised, Im running a mallory distributor that has a tach output wire.  The OEM tach replacement I have does not work when attached to it

Any bench testing/wiring instructions are appreciated

[highberg]

Hook green wire to any running engine ignition coil negative lead. Hook main power wire direct to battery. Keep tach from touching metal fender, etc while hooked up. Set it on a rag. Hook it up while engine is not running so no shock.

[DocMel]

Thanks   EXACTLY what I was looking for   Ill give a try this weekend

[MEK-Dangerfield]

So where is the ground connection?


I don't know anything about a Mallory set-up, but the tach has to have a ground connection from somewhere.

[highberg]

Factory tach shouldn't require a ground. Simular to a dwell meter (which is the same concept). Aftermarket have a ground mostly to support background lighting