Re: Adding Guages
The attached drawing shows the Model A electrical system in a simple diagram as Henry designed it. It is shown as a positive ground. By reversing the polarity designations at the battery it becomes a negative ground. It can be either six or twelve volts.
The way Henry designed it was his idea of theft prevention. The ignition switch when switched off puts a ground on the points. The wire from the ignition switch to the distributor is protected by an armored cable. The cable is attached to the engine with the number 8 head bolt. This makes it extremely difficult to hot wire a Model A. To do so you would have to unbolt the cable from the engine and remove the distributor to unscrew the distributor from the cable; then reinstall the distributor and screw in a bypass cable with a jumper wire that would clip on to the low side of the coil.
This design does not allow for any electrical accessory to be attached to the ignition switch because any device attached there would be drawing current thought the coil and be arallel the ignition points.
In order to have accessories attached to the ignition switch you would have to do some rewiring of the circuit. There would have to be a direct connection between the coil and the ignition points and the ignition switch would have to be above the coil and switch power to the coil on and off.
The Model A would them be easy to hot wire.
Tom Endy
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