Search the Community

I have a question for the electrical experts: I bought a Beck Arnley aftermarket ignition switch to replace the 40-year-old OE switch in my '70 Z. Seemed like a good preventative maintenance step, with the steering column currently out of the car. However, I've found puzzling difference in the operating logic of the two switches. It has to do with the switches' 'R' circuit, which I'm pretty sure means, 'Resistor' (as in, ballast resistor for the coil/tach circuit). With input power applied to each switch module by way of the 'B' (battery) terminal and output monitored at the 'R' terminal, this is what I find: Key Position "R' - OE Switch 'R' - Aftermarket Switch OFF dead dead ACC dead dead ON dead dead START live live to start, then goes dead when key is turned further against the detent spring It's been noted elsewhere that the Z's ignition circuitry is designed so that the ballast resistor is bypassed during engine start (so as to deliver higher voltage to the coil/points) and then brought back into the circuit during 'run' operation (so as to operate the points/coil at the lower, normal voltage). So a 'live' condition at the 'R' terminal of the switch means 'resistor out', whereas a 'dead' condition equates to 'resistor in'. My OE ignition switch adheres to this simple, two-step 'resistor out/resistor in' logic. The aftermarket switch does too... at first. But then as I twist the key a little further in the 'START' sector, working against the resistance of the internal spring to take the key all the way to the hard stop, the switch action reverts to 'resistor out'. This would typically be where the key would sit while cranking the engine (i.e. twisted all the way up to the hard stop) I'm not certain whether the aftermarket switch was designed this way on purpose, or not. There's also the possibility that it's just a defective unit. So now I'm not sure whether I want to use it. Does anybody have an idea about why the aftermarket switch would change from 'resistor out' to 'resistor in' halfway through the 'Start' segment? Could it be that this was done on purpose, so that the duration of the high voltage ('resistor out') condition in the coil/points circuit would be restricted to just the first part-rotation of the crankshaft, so as to avoid burning the points during prolonged cranking?