Simple Wiring Question

LeroyM

LeroyM

Senior Member
I'm trying to wire the Model A for 12 volts negative ground. I'm making it as simple as can be just to get it running for now, tell me if this is correct or not.

I have a 12 volt battery, the starter is connected to the positive on the battery. The wire coming off from the starter post is going to the positive on the coil. I have a red wire that is going from the positive on the coil to the key switch. I have a black wire coming from the other side of the key switch going to the distributor. The only other wire I have on the coil is on the negative side and that is going to the junction box on the firewall for ground.

Is this correct and will it run like this?
 
If I'm reading you correctly, no.

If you have an original popout switch: starter post to positive on coil, negative on coil to ignition switch terminal, then the armored cable will connect the switch to the points in the distributor.

But probably you have a replacement switch: starter post to one terminal of ignition switch, other terminal of ignition switch to positive on coil, negative on coil to points in distributor.

The coil gets its primary ground through the points.

Joe

Joe
 
Do not wire it that way. Looks like you have direct path from the battery thru the key sw to the points to ground. This will try to short the battery + to ground as soon as the points close.

Hook a wire from the starter terminal to the coil +. Then a wire from the coil - to the key switch that is hooked to the distributor points.

I used a simplier setup when just getting the engine to run in the frame. Used one of the armored cables sold to use with the replacement key switch that has a short armored section and a wire lug on other end. Hooked a wire wire with an alligator clip to the coil -. Screwed the one end of the replacemant cable into the distributor and hooked the lug to the coil +. Hook the clip to the starter terminal and you should have ignition. In the event of a problem, just yank on the wire to the starter terminal. I carry this as an emergency igniton system, no other parts needed.
 
I don't have a popout switch or the armored cable. So I need the wire coming off the starter post to go to positive on the coil, the red wire going to the switch on the negative side of the coil. After that I run the other black wire to the distributor that goes to the other side of the key switch?
 
NO!

You need to run the wire from the battery post up to the ignition switch. You can use one of the posts inside the junction box, if you want, but if this is just a test run of the engine and all these wires will be removed later, then you can run the wire straight up to the switch. Put a fuse in this wire, down close to the starter! If it only feeds the coil, (you don't have horn, headlights, anything else hooked up yet) it can be a small fuse (10A). Else make it a 30A.

Then you run a wire from the other side of the ignition switch (I am assuming aftermarket simple key switch with 2 connections) out to the (+) terminal of the coil, BUT, you must ADD an ignition resistor (pick up at NAPA) in the wire going from the ignition switch the coil.

Assuming the black wire going down to the distributor is connected to the points, the other end of that wire connects to the (-) post of the distributor. The (-) terminal of the coil does not connect directly to ground, it gets its ground through the points. I assume you also have a condenser in the distributor somehow? Need that too.

That should get you running.
 
Again, I'm not sure I follow that. You can do it two ways with a regular switch.

1) Battery to positive on coil; negative on coil to one switch terminal; other switch terminal to distributor. This is similar to the original wiring.

2) Battery to one switch terminal; other switch terminal to positive on coil; negative on coil to distributor. This has the advantage that you can turn other things on and off with the ignition switch.

Joe
 
LeroyM said:
I don't have a popout switch or the armored cable. So I need the wire coming off the starter post to go to positive on the coil, the red wire going to the switch on the negative side of the coil. After that I run the other black wire to the distributor that goes to the other side of the key switch?
Click to expand...

You can use your key switch to interrupt the power from the battery to the coil (+), OR to interrupt the connection from the coil (-) terminal down to the distributor. It is the same.

Ford interrupted the (-) terminal to distributor and left full power to the coil all the time.

I prefer to do it the other way around and use the key switch to take power away from the coil when I turn key off. (That is how "modern cars from the 60s and 70s were wired back when they had points, not electronics.)

HTH.
 
LeroyM,
if you are not sure i would get someone who know's a little more about elect. to assist. you,...you will probley come out cheaper, maybe a friend or car club near you.
[Im not a elect. but i have burned up a few dist, smoked a few wire's and blowen a few light's, Playing one]. Good luck.
 
What Joe said.
Battery, switch, coil, distributor are all connected in series and it doesn't matter which side of the coil is switched. Since it's a series circuit the switch will still open the circuit in the OFF position. As mentioned since it's being changed to 12 volts, I'd switch the power side of the coil so you could use the switch to turn other things on and off.
 
JoeWay said:
Again, I'm not sure I follow that. You can do it two ways with a regular switch.

1) Battery to positive on coil; negative on coil to one switch terminal; other switch terminal to distributor. This is similar to the original wiring.

2) Battery to one switch terminal; other switch terminal to positive on coil; negative on coil to distributor. This has the advantage that you can turn other things on and off with the ignition switch.

Joe
Click to expand...

Ok I follow what your saying and I'm going to go with option number 2. Now my question is this. I have the old loom that has the two wires in it were one wire runs to the starter and the other wire runs to the generator. Now I'm not worried about the generator right now.

Can I take the starter wire in the loom and go to the junction box terminal on the firewall, then run a new wire from that same junction box terminal were the starter is and go to my switch inside with everything else being the same in option 2 of Joe's example?

I know why make it more complicated but it would allow me to use the old loom on the side of the motor like the original.

Thanks for all the help everybody.
 
LeroyM said:
...Can I take the starter wire in the loom and go to the junction box terminal on the firewall, then run a new wire from that same junction box terminal were the starter is and go to my switch inside with everything else being the same in option 2 of Joe's example?...

Thanks for all the help everybody.
Click to expand...

Sure. If you have the top of the generator wire connected in the terminal box, you'll want to isolate the bottom of the wire, say with electrical tape, if you don't have the generator installed.

When you get the ammeter installed and wired, you might want to move the switch wire to the other terminal so the ignition draw shows on the gauge.

Joe
 
Make sure the generator output is hooked to the battery unless you have an electronic voltage regulator. If the generator is run with the output open, you will fry it.

If you don't have an EVR, you can short the output terminal of the generator to ground without damage.
 
To change form positive ground to negative ground; Take a look at the drawing. Change (swap) the wires on the battery, amp meter, coil, and away you go!

Now to change from 6 to 12, change all bulbs, rewire or get a resistor for the horn, replace or get a resistor for the coil the starter will be fine.

I don't think I missed anything, oh yea, if you are going to an alt and plan to add accessories such as radios and hi power headlamps you may want to replace the amp meter with a 30 - 30 in place of the 20 - 20.
 

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Roadster62 said:
What is the point of changing to 12 volt? NAPA and other parts stores sell 6 volt batteries.
Click to expand...

I agree and I like the way my car starts in one or two compression strokes with no HARSH bendix engagement, and I like my bright lights using 6 volts and original bulbs and generator.
 
I'm changing to 12 volt because I'm going to a electronic distributor sooner or later. Also 6 volt batteries tend to die down faster then the 12 volts and a quicker start makes it nice to.

I'm still going to be using a generator with a electronic voltage regulator inside of the cutout from funproject that I got.
 
I'll never understand electricity, the more I read the more confusing it gets. I'm a body & paint guy, they don't have to run to look good to me.
 
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