1969 Camaro SS 350 factory tachometer

[wmlhhr2006]

My factory tachometer is giving me the fits, i.e., it just recently started fluctuating all over the place when I turn on turn signals, hit brakes, turn on lights etc., it reads fine when none of the items mentioned take place. Any help in this area would be appreciated greatly.

Thanks

[WayneinNZ]

Check your ground conection to the dash.

[wmlhhr2006]

That makes sense but not being familar with electrical systems, where exactly do I check the ground to dash out?
Thanks
Bill

[JohnZ]

That makes sense but not being familar with electrical systems, where exactly do I check the ground to dash out?
Thanks
Bill

The instrument panel harness ground is screwed to the bottom of the steel instrument panel, below the headlight switch - has two wires - one from the harness, and one from the headlight switch. Shown in the Assembly Manual in UPC 12, sheet B5, lower right corner of the illustration.

[wmlhhr2006]

Thanks for the help, also, ordered the factory assembly manual from faxon today which should help with educating myself on this topic and many others as well!
Thanks again
Bill

[wmlhhr2006]

I located the panel harness ground and it is connected properly, nothing loose or disconnected, is it possible the tachometer itself is starting to go out? Maybe I could hook up an external tachometer to see if I would get the same erratic readings from it and if not then maybe its the tachometer. Any other thoughts or ideas would be appreciated very much!
Thanks
Bill

[69pace]

Yes you could swap in an working OEM Tach, but just be aware that most aftermarket Tachs will require that you use a filter if you have stock dizzy and ignition.

A more difficult procedure would be to bench test your unit but If you have a sinewave generator, or access to one you can bench test the unit.

I would double check your Voltage Regulator and Alternator outputs and check the wiring connection at the fuse block and the back of the tach, and the brown wire out to the coil.