[B_man_Al]

Hi George ...

I just did the experiment I suggested to you in post 76 with my model B, 1.5 ohm ballast, 1.5 ohm coil. Here's what I got using a digital multimeter.

1-Ignition off: V across ballast measured = 0 V
Comments - makes sense, as no current flowing

2-Ignition on, points open: V across ballast measured = 0V
Comments - makes sense, again as no current is flowing

3- Ignition on, points closed , engine off: V across ballast measured = 6.3V
Comments - makes sense, current is flowing and is 6.3V/1.5 ohms = 4.2A

4- Ignition on, engine running, points pulsing : V across ballast measured = 2.3V
Comments - If the voltmeter was reading correctly, and could read the peaks, it would read higher than case 3 by about 16% because of the increase in battery voltage from 12v to 14v. This would make it 7.3V instead of the measured 2.3V.

Thus the real coil current is about 7.3v/1.5 ohms=4.8A. This is what you would actually see if you made the measurement with an oscilloscope

However because of the averaging going on, there is a large error in the measured voltage, leading to the conclusion that the current is only 2.3v/1.5 ohms = 1.5 A. rather than 4.8A as calculated above.

Hope this helps to confuse the discussion some more :-)