Non Impulse Magento QOD

Rich Holt

Rich Holt

Line Up and Wait
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Can not grounding the ignition switch properly hurt the magneto? I recently discovered that my new ignition switch was not grounded correctly and now then the Magento died. Just curious if the one could have caused the other, or if it is possible/probable for both magnetos to fail at the same time.
 
It’s possible. Not too likely but possible. P-leads didn’t ground? Intermittent ground?
 
skyking3286 said:
It’s possible. Not too likely but possible. P-leads didn’t ground? Intermittent ground?
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What’s the Mechanism? What actually dies in the mag and how?
 
Considering the fact that the breaker points are grounding and ungrounding the primary winding dozens of times per second during normal operation, it seems highly unlikely that an errant ground from the P-lead would do any damage. OTOH, a defective ignition switch could conceivably connect the battery voltage to one or both primaries and burn up either the coil or the points.
 
Another great reason to fly a non electrical Aeronca!
 
flyingbrit said:
Considering the fact that the breaker points are grounding and ungrounding the primary winding dozens of times per second during normal operation, it seems highly unlikely that an errant ground from the P-lead would do any damage. OTOH, a defective ignition switch could conceivably connect the battery voltage to one or both primaries and burn up either the coil or the points.
Click to expand...

That's how a coil/points ignition works. But magnetos are excited by a magnet passing the coil. No electricity from anywhere else is required. I'm still not sure how a bad or intermittent ground can damage a mag? I'm hoping for education...
 
The older (pre-1976) automobile ignition is often called battery ignition. Both it and a magneto have points and a coil. The difference is how the coil primary is "charged" with current. With battery ignition, when the points are closed, current from the battery flows through the coil. In a magneto, when the points are closed they "short circuit" the coil primary. When the magnet passes by a high current is developed due to the short circuit. In BOTH systems, when the points open a medium voltage (about 100V) is developed due to the current being interrupted in the coil primary. This voltage is stepped up to several thousand volts in the secondary winding of the coil.

I said that magneto damage due to an intermittent P-lead ground is "highly unlikely" because never say never. Realistically it is impossible.
 
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