Hooking up electrical tach

Brother Hesekiel

Brother Hesekiel

Senior Member
A while ago I received my period-correct APCO dual gauge bracket (mounts to the bottom of the steering column) and APCO mechanical temperature gauge and installed everything. Looks and works great!

Now I want to put my old tachometer in the "right" hole but I don't know where to find ignition power. The way I see it, the car is constantly hot, when the battery is hooked up. I have a main power switch mounted with a bracket to my steering box, but if I turn main power on, I have juice everywhere, on the lights, the horn, interior light, and, of course, the junction block. I'd love to get only power to the tach when the ignition is turned on, but I'm not sure if that is an option. If it is, where would I hook it up?

Thanks!
 
A little more info would help:

1) Are you 6V or 12V
2) Gen or Alt? If alt, what type - 10/12SI, other, single or 3 wire?
3) Original popout switch or non- popout replacement?

A solution can be had for any, but it depends on what now exists.
 
Brother Hesekiel said:
A while ago I received my period-correct APCO dual gauge bracket (mounts to the bottom of the steering column) and APCO mechanical temperature gauge and installed everything. Looks and works great!

Now I want to put my old tachometer in the "right" hole but I don't know where to find ignition power. The way I see it, the car is constantly hot, when the battery is hooked up. I have a main power switch mounted with a bracket to my steering box, but if I turn main power on, I have juice everywhere, on the lights, the horn, interior light, and, of course, the junction block. I'd love to get only power to the tach when the ignition is turned on, but I'm not sure if that is an option. If it is, where would I hook it up?

Thanks!
Click to expand...

That's correct on a stock setup there is power "everywhere". The sealed popout switch's key, when turned on will remove the ground from the points, and switch power to them instead.
 
If you are using the stock ignition set up, the easiest way to power the tach is to use a separate toggle switch for the tach. I ran mine that way for a couple of years until I changed out the repro pop-out switch that really didn't work very well anyway.
 
Mike, I have 12V, negative ground, alternator, and aftermarket, non-pop-out switch. My excuse: I bough it that way!

A-alternator.jpg
 
If you have an aftermarket on/off key switch with two terminals on the back the job is easy. Just change a few wires to turn the coil on/off with the switch. (Your car may already be rewired that way to turn the coil on/off)

*** BEFORE starting, make a detailed drawing (or take pix!) of how everything is now connected.***

1)Remove the two wires connecting to the coil primary terminals.
2)From the yellow/black wire connection side of the terminal box run a wire to the key switch, either terminal.
3)Wire the 2nd switch terminal to the + side of the coil primary. (In your case the switch output wire goes to the + coil side because you converted to 12V neg ground, and the key switch output will be +).
4)The other side of the coil primary connects to the wire going to the dizzy points.
5)Test, car should run/stop with key on/off.

Now, anything you want switched on/off (tach, electric fuel valve, radio, etc.) connects to the 2nd switch terminal.

I hope this helps. Clear as mud? Draw it out, it will make more sense, maybe.:o
 
What you see is "leftover" stuff from when I flushed the radiator with a garden hose. I wasn't kidding when I -- in another post -- stated that I haven't washed my car since the day I brought it home and thoroughly pressure washed it. Looks worse in the dark using a flash though!

Now there's clean water in the system.
 
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