Neg ground wiring system?

[Frank Wilkie]

On a 6 volt neg. ground system, when wiring up the ignition from the key switch to the coil which side of the coil do you wire to, the positive or neg. side?  Or does it make a difference?  This is on a 1928 Diamond T truck.

[ipeeforward]

Hi,

This article may help.

https://mgaguru.com/mgtech/ignition/ig104.htm

 

[padgett]

In general, points ground (why just one wire). Points wire would be on the negative side of the coil.

[Frank DuVal]

And ignition switch to the positive terminal.

 

Makes a difference in top end performance. Even if the vehicle is not known for top end performance....👍

[Frank DuVal]

Question has been answered, so here is the science behind the answer. 

 

The ignition coil is a transformer, and produces an output of polarity with respect to the marked input terminals. Not to confuse, but the secondary side is always negative with respect to ground*, ground being the case of the coil. This is because those little electrons flow from negative to positive (thank Ben Franklin for this seeming error), so in jumping the spark plug gap, it is easier for the electrons to leave the center electrode and be attracted by the large grounded electrode (also think of the gimmick spark plugs with multiple electrodes which make this more possible paths for the spark to hit).

 

So you want the + and - of the primary terminals to match the battery polarity so the secondary is the correct polarity also.

 

This is also  why the car will start and run, just lose top end performance, with reversed coil polarity, since that is where the most voltage is needed to fire the plug, and now the spark has a hard time finding that little center electrode.

 

 

 

*Up until they invented high energy output coils/ignition systems (think HEI) and wired two cylinders in series to one coil. In this case, one spark plug is firing the wrong way, but there is enough energy to accomplish this WELL.

[Frank Wilkie]

9 hours ago, ipeeforward said:

Hi,

This article may help.

https://mgaguru.com/mgtech/ignition/ig104.htm

 

thank you ,, it did

[1937hd45]

The more I read about electricity the less I understand, it is like the snake house at the zoo. Hate snakes, but have to walk through the place.

 

 

Bob