Aside from a few wires that needed attention, the electrical system has been pretty solid for a 1972. After spending a little too much time reading the postings on melted wires and engine fires, I thought I would bring up a new discussion to alleviate my newfound paranoia. :eek:

On the off-chance that my resistance wire to the coil (points ignition) fails, I would like to be able to run a wire from the battery to the coil so I can limp home. :D

I know that 12v is too much for the points, so I wired a Mopar Ballast resistor in series going to the + side of the coil. When I measured the connector on the other end of the wire (not connected to the coil), I got 12.08v. :confused:

I would expect it to be less. What gives? I also noticed that the ballast resistor was pretty hot.

Did I have it backwards? I connected the + side of the resistor to the bat. and the - side to the + side on the coil? Any ideas?

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-Henry

The points are not going to burn up running the car on 12 volts or even 16 volts. As long as the capacitor (condensor) is good they will last almost as long as running them at the reduced voltage. Reducing the voltage was meant to extend the life of the coil.
What ruins points or any switch contact is arcing as they open and close. The condensor reduces the arcing.
If I had a problem with the resistor wire, while on the road, I would wrap a wire under the battery positive side post terminal and tighten it underneith. Wrap that wire around the heater hoses so it stays out of the engine. The other end of the wire would go to coil (+).
If you need to shut the engine off, this wire needs to be disconnected.

I know that 12v is too much for the points, so I wired a Mopar Ballast resistor in series going to the + side of the coil. When I measured the connector on the other end of the wire (not connected to the coil), I got 12.08v.
Voltage does not drop when it goes through a resistor unless there is more demand for electric than there is supply. With points open, the engine not running, and with the ignition on, there will be near battery voltage at the + coil connection no matter what resistor wire or resistor there is in the circuit. When the engine is running there will likely be about 9 1/2 volts at the + coil connection due to voltage grounding through the points. Any one want to bet with me? Don't just think you know the answer, check it for yourself.

I lost $10 to an electronics geek years ago on just this subject. graemlins/clonk.gif Also with 16 volts and points, condenser requirements are different than they are with 12 volts.

Willing to bet the contacts can handle greater than 100 VAC @ the required amperage. Takers?

Thank you all. The impressive body of knowledge never ceases to amaze me.


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It's that E over I x R stuff again. That magic little "Eddie Electron" doing his thing.

(and yes, it will show battery voltage because it's not under load)