Autometer AutoGage #2300 Issue - "Click" and Needle Drop Every 13-14 Seconds, But No Engine Stumble or Change in Sound

[Duster256]

Installed on a 1971 Duster 340, my tach was operating fine until today when I noticed an periodic audible "click" and momentary needle drop, occurring about every 13-14 seconds. In "Drive" and holding the brake, the tach needle momentarily drops from 750 to 400 and back up to 750. In "Park" and holding RPMs at about 1900, the needle momentarily drops to about 1000 and back up to 1900. But the strange thing is that if you listen to the motor, there is no stumble or change in sound when the momentary needle drop occurs - which leads me to believe it might be an electrical issue with the tach? I've reached out to Autometer's tech support and am waiting to hear back from them. FABO Nation - any ideas what might be causing this click and needle drop every 13-14 seconds? Grounding issue? Thanks, Dave

 

[GTX JOHN]

You should easily hear that big a drop in RPMs.

If you do not detect it, My guess is the problem is
electrical.

 

[Demonracer]

What tach are you running, and have you double checked all if the wires carefully?

 

[Oldmanmopar]

Where is the click sound coming from.

 

[Newbomb Turk]

What ignition do you have and where is the green wire from the tach hooked up?

 

[Duster256]

Where is the click sound coming from.

My apologies, the click is coming from the tach

 

[Duster256]

What ignition do you have and where is the green wire from the tach hooked up?

Green wire is to the neg side of the ignition coil

 

[Newbomb Turk]

Green wire is to the neg side of the ignition coil

WHAT IGNITION? If you have a box that has a tach output you need to hook the green wire there, not to the coil.

 

[Duster256]

WHAT IGNITION? If you have a box that has a tach output you need to hook the green wire there, not to the coil.

Turk, my car as purchased from the prior owner has no box with a tach output, thus the ignition coil tap. As I mentioned, it was running fine (as is) until recently. The other day I redid the ground connection and that seems to have solved the click/needle drop issue. Than

 

[Duster256]

I redid the tach ground connection and no more click/needle drop. Thanks FABO Nation for your tips!