Model T Magneto- How to Test

[@dalebertdurando1496]

The 1156 is a 12.8V bulb, so I'm guessing the voltage using a meter is probably 6 to 12 Volts depending on the rpm. This likely is near the same voltage as using a battery. Each coil box draws about 1.3 amps, so the magneto should be able to produce at least that amount of current. The 1156 draws about 2 amps, so its a good test.

[@tbugger]

Dale- the test is to see if the magneto is strong enough to blow the bulb. A weak mag will light the bulb- but not blow it. TWO reason the bulb blows is because the Ford magneto produces AC voltage (not DC like the battery) and second a strong mag will produce 30v + or -. Again, that voltage is AC.

[@EdwardZUCAL]

You say that it is running on Mag when you are doing the test. Are you starting it on bat then switching to mag to do the test.

[@billrobinson2050]

Yes, start on batt, then switch to mag, however if the mag is in good shape it will start on mag too.

[@FREDRICKPOLLY]

Cool test. Is the engine running on the mag at the same time your doing the test ?

[@tbugger]

Yes, the engine IS running on magneto, but the bulb will blow whether the engine is running on mag or batt. Just do NOT allow battery DC current to enter the magneto's AC current at any time. Bad news if you do. Credit should be given to the MTFCA Forum for this test. I just created a video for it.

[@FREDRICKPOLLY]

tbugger thank you for the video and the info. It’s great that like minded enthusiasts can help each other out. 👍