Wire sharing

[pflaming]

Question. There is a single wire from the ign to the coil , IF that wire is cut and a second wire to elsewhere is added, does that diminish the total power to the coil? 

[Dave72dt]

It's possible to damage the ign circuit by attaching a higher resistance application into the ignition wire than it was designed to carry.  Any number of applications can be powered up from the ign side of the switch but wouldn't recommend doing so by spitting the ign wire.  At the most, maybe a trigger circuit for a relay but then why not feed it from the switch as well.

 

FYI, Ford, for years ran 2 wires to the coil on their 12v systems.  One wire was a resistance wire designed to reduce voltage going through the points when running.  The other wire was full battery voltage to the points when the starter was engaged to improve starting.  You have to remember that when the starter is engaged you get a voltage drop in all the circuits including ignition so now the battery is providing approximately the same voltage to the points when in starting mode as it does when in running mode, hence, theoretically better spark, better starting.  Whether or not that is indeed what happens, that was how it was explained to me years ago and I've never tested it but understanding the theory makes troubleshooting easier.

 

It sounds like you may still be chasing your coil or starting issues.  If so, detailing the damage to that cap and what you checked/tested/proven correct may let us assist.

[pflaming]

1. I had a 10 amp fuse on the wire from the battery terminal to ign, a protection for the harness, and two I split off a wire from the power wire to the coil. Corrected those just before dinner time. So no test yet.

Edited February 28, 2021 by pflaming

[Sniper]

It depends.  In a parallel circuit voltage remains the same, but current will vary.  As long as the supply wire can handle the required current draw for both circuits, then no it will not affect anything.  If the supply wire is undersized then yes it can affect both circuits.

[Dave72dt]

I've got a new harness (slowly) going into my current project.  The instructions suggested the use of a 10 amp charger to power up and test the harness instead of using the vehicle's battery.  It's enough power to test and has it's own circuit protection built in.  Just a thought.

[pflaming]

Nearby, I knew they owners, a fruit packing plant was adding a fourth large cold storage room. The insulatin was a sprayed on foam, highly flammable. They had it closed off for the foam to breath when xsomehow I jolt of electricty went into it.  It exploded, and sent a short back into the adjoining cold storages which sent a jolt to the packin room circuit panel which exploded, in less than 20 minutes the entire facility was ablaze, the workers literally ran for their lives.

  In three hours those steel buildings litteraky burned to the ground. The fire was so hot, they recovered nothing!  Thus I respect hoy electrical wires! 

[Sniper]

Heck, a 9v battery is enough to test with and nowhere near a 10A supply so less likely to cause issues.  When I rewired my 51 I used nothing more than my multimeter on the ohms setting, that's powered by the 9v battery in the meter.  The only issue I ran into was when the fan was on high and I shut down the engine it wold kick the starter on.

 

Not sure what is going on there but a diode fixed that.  

[pflaming]

Been a while. Don’t work very fast anymore. Time has caught up with me. 
 

I just learned that the coil must be in polarity with the battery. I don’t understand polarity. So researched it, answer, if the battery  is negative ground, then the wire out of the coil to the distributor must come from the negative post.

 

what difference does negative ground vs positive ground make? I’m negative ground now. 

[Sniper]

The effects of polarity of the coil being wrong really depends.  When I got my 51 it was still a 6v positive ground setup, but the coil was installed backwards.  Ran fine. 

 

Years ago I had a neighbor kid trying to get his VW bug running and couldn't.  So I headed over to see if he wanted help.  As it turns out his aunt had done a tuneup on it and it wouldn't run, ran before that.  Being that it was a points ignition my first though was that the points gap was wrong or shorted.  Looking at the setup I saw the coil was wired backwards and it had a very weak spark.  Swapped polarity (hooked the coil - to the points) and it fired right up and ran.

 

So it really depends on the system involved, I guess.

[greg g]

Supposedly  DC electricity actually travels naturally from negative to positive instead of the way we have trained our brains to perceive  plus is better than minus and therefore has it way with minus. And since the loads don't care which way it's flowing, the biggest benefit was that it slowed the accumulation of battery terminal goo growth and corrosion at connections through the system..  We all know 6v likes clean solid connections.  Was told in auto shop many years back that if wired against the system polarity, the coil would be prone to weakened spark at higher rpm.  Since most of use don't intensuallly explore the top of our rpm range the problem is moot in normal operation unless the coil is near replacement,  then it's breakdown would 9occure at shorter dwell times.

[Frank Elder]

On 2/28/2021 at 4:13 PM, pflaming said:

Nearby, I knew they owners, a fruit packing plant was adding a fourth large cold storage room. The insulatin was a sprayed on foam, highly flammable. They had it closed off for the foam to breath when xsomehow I jolt of electricty went into it.  It exploded, and sent a short back into the adjoining cold storages which sent a jolt to the packin room circuit panel which exploded, in less than 20 minutes the entire facility was ablaze, the workers literally ran for their lives.

  In three hours those steel buildings litteraky burned to the ground. The fire was so hot, they recovered nothing!  Thus I respect hoy electrical wires! 

Were they cat owners?