9N coil problems...

[B.Y.]

Facts & thoughts out there? A friend of mine has a 9N and is replacing coils 1x a year. Any ideas amongst you guys? The machine is still a 6V generator system. Could it be the quality of the coils he is using? Thanks for your considerations!

 

[Bruce (VA)]

It could be the coil, but more likely than not, it's either the absence of a resistor, a burned out resistor or a bypassed resistor.......or, he is leaving the key on.

Technology & materials being what they were in the 30's, that square coil would melt if it ran on much more than 4 amps for any length of time. (see tip # 38 for an example). In order to get a hot spark at the same time the starter was drawing max current from the battery, a ballast resistor was added in the ignition circuit. What that did was add about .3 ohms of resistance in the circuit, added to the 1.5 ohms of the coil. That got you 3.5 amps or so at start up. As the voltage increased when the engine was running to about 7.5 volts, the resistor heated up, adding more resistance in the circuit. 1.0 ohms hot, plus 1.5 ohms of the coil got you down to 3 amps or so to keep from melting the coil.

First, make sure he understands that leaving the key on w/ the points closed will melt the coil in about 3 minutes. If that's not the problem, he should make sure it has a resistor & that it's not bypassed. Then, measure it w/ a meter. It should read about .3 ohms cold. Then, measure the coil. It should read from .5 to 1.5 ohms.

50 Tips

 

[Dave in Utah]

BY,

I went thru 2 coils when I got my 9N last spring. After the 2nd one, I started looking for the "infamous ballast resistor" and couldn't find one. Place for one on the back of the dash.

I put one in and haven't had a problem all summer.

Dave

 

[FatTony]

Best place to start is make sure the resistor is in line and in good shape. It either works or it doesn't. I know from sad personal experience what happens in the "doesn't" case.