12 volt negative ground tachometer wiring on 1929 model A

[31Deroadster]

I converted to a 12v negative ground system on my 29 A and am wanting to hook up a 12v tachometer but am not sure how to correctly wire it in. The Tach is from Snyder’s and I have all brand new wiring in the entire car. I also am running an alternator instead of a generator. Please don’t bash me on doing the 12v conversion. Already got enough flack from the Di-hard A’ers. Thanks for any assistance. Probably stupid easy but just want to make sure I’m wiring it correctly.

[McMimmcs]

welcome to the Barn. I’m sure you’ll get the information you need. Wayne

[GRutter]

One lead to ground, the other to the point-side of the coil

[Tom Endy]

I installed a tac in my 6-volt positive ground Victoria. A 12-volt version would hook up the same way. The two leads from the tac go to the two primary terminals on the coil, just observe polarity.

The attached article is about my installation.

Tom Endy

[Bob C]

Did you see the instructions on Snyder's site?
https://www.snydersantiqueauto.com/R.../A-12120-B.pdf

[31Deroadster]

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I have those but stupidly am not sure which is the point side of the coil. Red lead from key is on the positive post and the negative post goes to the terminal block post. The armored cable goes to the distributor from the other side of key.

[Bob C]

If the ignition switch is wired as original then sounds like the coil is wire backwards
for 12V negative ground.

[Y-Blockhead]

Originally Posted by 31Deroadster

I have those but stupidly am not sure which is the point side of the coil. Red lead from key is on the positive post and the negative post goes to the terminal block post. The armored cable goes to the distributor from the other side of key.

Originally Posted by Bob C

If the ignition switch is wired as original then sounds like the coil is wire backwards
for 12V negative ground.

Bob C is correct. Negative ground, coil negative to points via ignition switch. Red wire should be on coil negative terminal in 12v system.

[tinkirk]

Normally it goes
Red to 12v ing.
Black to ground
Green to - neg side of coil
Yellow is for the light


Sent from my iPhone using Tapatalk

[Y-Blockhead]

Originally Posted by tinkirk

Normally it goes
Red to 12v ing.
Black to ground
Green to - neg side of coil
Yellow is for the light


Sent from my iPhone using Tapatalk

"Normally" I would agree with you but the tach the OP is asking about only has 2 wires...

[Johnny Nitro]

Originally Posted by Bob C

Did you see the instructions on Snyder's site?
https://www.snydersantiqueauto.com/R.../A-12120-B.pdf

This

[Steves46]

My Model A was converted to 12V and will be installing a Bosch Retro Tach which comes with 4 wires. Although I know where to connect the Ground, Light, and Signal wires, I am not sure about the Power wire. My Les Andrews Book (Vol II) in the Tachometer Installation section calls for the Power wire to be connected to the passenger side Terminal Box Post however when I put my test light on one of the already connected wires, it lights. Since the Bosch instructions call for the Power wire to be connected to any wire that is energized ONLY when the ignition is on, I am reluctant to go by the guidance in Les Andrews book. Maybe I am wrong but would greatly appreciate any guidance and Merry Christmas. Best, Steve

[Y-Blockhead]

Originally Posted by Steves46

My Model A was converted to 12V and will be installing a Bosch Retro Tach which comes with 4 wires. Although I know where to connect the Ground, Light, and Signal wires, I am not sure about the Power wire. My Les Andrews Book (Vol II) in the Tachometer Installation section calls for the Power wire to be connected to the passenger side Terminal Box Post however when I put my test light on one of the already connected wires, it lights. Since the Bosch instructions call for the Power wire to be connected to any wire that is energized ONLY when the ignition is on, I am reluctant to go by the guidance in Les Andrews book. Maybe I am wrong but would greatly appreciate any guidance and Merry Christmas. Best, Steve

Steve, I got your PM... email me. For some reason I can't get the schematic bigger