rvirgil_KS said: (quoted from post at 15:51:21 05/02/09) In a 6 volt system when the points close current flows through the points, coil, and switch, to the battery. The issue is amount of current flow. The circuit (points and coil) is designed for a maximum of 3 to 4 amps of current.
When battery is increased to 12 volts the 6 volts is doubled and so is the current, exceeding the design of coil and points. Excess current will soon destroy both. A ballast resistor approximately equal to the resistance of the coil primary can be added in series between coil and battery. This drops 6 volts across the coil and 6 volts across the resistor maintaining the 3 to 4 amps of current.
Or with 12 volts, a true 12 volt coil (primary of coil wound for 12 volts rather than 6 such as NAPA IC14SB)can be used without the need for a resistor. It's internal resistance limits the 12 volt system to 3 to 4 amps.
With current held within design limits the points and condenser will work with either 6 or 12 volt supply.
The current flowing in the circuit is governed by voltage and resistance, the dwell time is irrelevant.
I would like to add that Dwell time is not irrelevant, as stated with 12v going to a 6v coil the dwell time is more than needed therefore leading to a heating of the coil and therefore shortening it's life, there are two options to fix this
1. Shorten the dwell time, not that easy on an old non electronically controlled system OR:
2. Add resistance to the system therfore reducing voltage and amperage back down to a safe level because we all know that Current = Voltage Divided by Resistance and also Voltage = Current multiplied by Resistance.
If you could cut the dwell time in half then the system would be perfectly happy at 12v with no resister.
This post was edited by ih560 at 18:30:26 05/03/09.
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