Tachometer Hooked Up But Still Not Working

[boboh1]

The PO installed a new aftermarket clock/tach in my 1969 Superbee. I verified the connections to be correct but it still does not function. On the back are some nuts marked with a ‘G’ by each one. Is this for a ground? Do I need to run a wire from one of these posts to a ground connection? Thanks.

 

[Black_Sheep]

One wire supplies 12V+ to the gauge, I would assume that the other wire is the tach signal. The absence of insulating washers on the other terminals leads me to believe that the gauge grounds through the case. The case has to be somehow grounded to complete the circuit in order for it to work. How is it mounted? I would ground the case with a jumper wire and see if it works…

 

[boboh1]

Yes the blue wire is connected to positive and the other to the coil. I’ll try grounding the case to a metal ground and see.

 

[pnora]

What ignition system are you running?

 

[boboh1]

Stock except for Pertronix in place of the points/condenser.

 

[velocityss1985]

The tach housing grounds to the dash cluster. The studs with a "G" are grounds to the tach housing. + is keyed ignition and the other one is the tach signal. Make sure the signal wire is on the negative side of the coil. I have a re-pop one as well and mine took a **** after 500 miles. So now I have to replace it. If it has power, ground and signal it should operate, if not there is an issue on the inside board.

 

[pnora]

I have several old tachometers as well as meters. I plug them on the tachs wires to test the operation. If they work then the problem is in the cars tach.

 

[MWbirdLOVER70]

One wire supplies 12V+ to the gauge, I would assume that the other wire is the tach signal. The absence of insulating washers on the other terminals leads me to believe that the gauge grounds through the case. The case has to be somehow grounded to complete the circuit in order for it to work. How is it mounted? I would ground the case with a jumper wire and see if it works…

Case grounds once mounted from what I’ve seen

 

[boboh1]

It seems like it may be the tach itself.

 

[Billccm]

Here's a series of videos that will help you understand the tach operation and upgrade to electronic.

Restoring Tach for 68 Road Runner – Project BeepBeep