ignition ? on model 50

[55 50 Ron]

Setup is normal 12 VDC positive ground with 6 volt coil.

engine stopped, points closed, ignition switch on, I measure -4.3 VDC on coil primary minus input.
Seems it should be closer to 6 VDC. I haven"t measured the ignition resistor.

Engine running, about -9 VDC on coil primary minus input. Seems too high.

Above measured with Fluke 73 III multimeter

Comments good or bad. Thanks

 

[Bob]

Sounds typical to me. May I inquire as to what problem you are experiencing?

 

[John T]

Im kinda likke Bob, Im not all that concerned with your readings and the difference in static versus operating voltages has to do with the characteristics (response time and damping etc) of your meter and likely to some extent the RPM and points open/close duty cycle. Perhaps an ammeter reading to measure coil and points current as the system is designed so the points dont have to switch too much over 4+ amps else they can burn prematurely. Maybe like the old saying goes "if it aint broke dont fix it" lol If you were having problems like the points were burning up quickly (too much current) perhaps the ballast is too low resistance?? (kind of agrees with that 9 volt reading)

I just hear so many difference with say an old Simpson 260 analog meter versus a modern digital meter that Im reluctant to give a quick diagnosis!!!!!!!!! I JUST DONT KNOW WHAT IF ANYTHING IS WRONG other then too much current (too low ballast resistance or a coil problem) will burn the points too quick

John T

 

[55 50 Ron]

My old coil was sometimes firing across from the high voltage to a primary terminal and was kind of hard to find.

A new coil was installed and while I was at it, I decided to make a few measurements and was mildly surprised by the measurements.

 

[Anonymous-0]

As John T says... that running number has a lot to do with duty cycle. For example, with the engine running if the voltage is 6 when the points are closed and 12 when open and the duty cycle is 50% (half the time they are open, half the time closed) the Fluke may very well register 9 volts, the average of the two! As John T said, I'd be more concerned with the current through the coil.