MTFCA Forum

My 1915 Touring has been running great until today. I always start on battery and switch to magneto and the car runs with no problems up to now. Today, I started and ran fine on battery but when I switched to magneto, the car immediately stopped running. I am going to pull the magneto post and check to make sure that it is clean. Is there anything else I should be looking at that could make the power from the magneto suddenly stop?

Any help will be greatly appreciated.

Pull the mag post 90% that is it, another is the wire in the back of the switch, ohm it out.

Might be that your crankshaft endplay has been "marginal" for some time, and then all of a sudden conditions caused it to be a bit more than "marginal",.....???

Either something damaged the field coil or the terminal is shorted. I would pull the terminal off first and make sure it's clean and doesn't have little on it.

Stephen

Either something damaged the field coil or the terminal is shorted. I would pull the terminal off first and make sure it's clean and doesn't have little on it.

Stephen

David, take the wire off the mag. get a DMM or other means of testing AC volts, start the engine & check to see if you have any output from the mag if you have good AC volts out of the mag look for other issues if not take the trans cover off and look for things that should not be in there before proceeding to the next step. ie. shorts & opens.

Craig rather than a DMM I use a 12v bulb 18 watt bulb.
Bulbs give all the info you need, essentially a perfect GO/NOGO test.
DMMs often get confused by the nasty non-sinusoidal waveforms put out by the magneto and the rotten DC put out from the generator.

Stephen:

The magneto post if measured for resistance to ground will fool you into thinking something is wrong there when you measure a dead short. The total resistance of the magneto coil from the post to ground is typically .25 ohms - yes 1/4th of an ohm which is usually less than the resistance of the probe leads from the meter so a reading of 5 ohms is not uncommon. To get a more accurate reading you need to touch the test leads together and see what the reading is. Subtract that number from the reading you get with the test leads then connected to the mag post and ground. That will be in truth about 1/4 Ohm.

I agree with others to check the mag post directly for AC voltage with nothing connected to it and the car motor running on battery. Of if you get a reading above 20-25VAC with no load then try an 1156 bulb or other 2 amp 12V bulb as a load and measure again. If you still get a really bright light and burn out the bulb then your issue is a connection in ignition switch or wiring path.

hope this helps.