While the engine was running .....
The battery + to ground should stay fairly constant. Maybe vary by a few tenths of a volt as the points open and close if the battery didn't have much of a charge. I'd expect to see around 13 volts here. You should see the same on the battery side of the ballast resistor to ground.
If the meter was hooked to "both sides of the ballast resistor" I'd expect to see the voltage to jump between zero volts when the points are open and 4 to 6 volts when the points are closed. Because your meter probably updates 5 or so times a second "your mileage may vary".
If the + meter lead was hooked to the coil side of the ballast resistor (or the + side of the coil) and the - meter lead was on ground I'd expect to see the voltage to jump between zero volts when the points are open and 7 to 9 volts when the points are closed. "Your mileage may vary".
Error in the previous statement. It should read ...
If the + meter lead was hooked to the coil side of the ballast resistor (or the + side of the coil) and the - meter lead was on ground I'd expect to see the voltage to jump between 13 volts when the points are open and 7 to 9 volts when the points are closed. "Your mileage may vary".
If the + meter lead was hooked to the coil - side and the - meter lead was on ground I'd expect to see the voltage to jump between 13 volts when the points are open and 0 volts when the points are closed. "Your mileage may vary".
Last edited by Bill Hanlon; 09/02/2024 10:22 PM. Reason: Incorrect information
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
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