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If your combustion engine isn’t igniting, is a faulty magneto coil to blame? Schott Magnetics, the leader in custom magnetics manufacturing, will answer that question and more before giving you a step-by-step guide to teach you how to test a magneto coil with a multimeter to tell if it has a short. 

What Is a Magneto Coil?

A magneto coil is a permanent-magnet generator. Its main use is to ignite compressed gasses in internal combustion engines, like those used in tractors and chainsaws. 

How Does a Magneto Coil Work?

Magneto coils contain three components that work together to create electricity:

 

  1. Armature: A u-shaped component with a main coil of thick wire and a secondary coil of thin wire.  
  2. Flywheel: Creates a magnetic field around the armature by using two strong magnets.
  3. Electric Control Unit: Breaks up the electromagnetic field and directs the resulting electric energy away from the magneto coil to wherever else it’s required.

 

Magneto coils work by utilizing the magnetic field within the coil’s vicinity to create an electric current. This happens when the coil moves (or the flywheel rotates between two magnetic poles) to create an electromagnetic field. That field is then interrupted, making an electrical voltage. Contact to the armature is broken, and the electromagnetic field reproduces a pulse of electricity that is directed to a spark plug.

Where Are Magneto Coils Used?

Magneto coils are used in many different industries, including industrial and aerospace. They are used for ignition of compressed gasses in combustion engines, like:

 

  • Large gasoline engines for vehicles, industrial equipment, light aircraft, etc.
  • Small gasoline engines for RC model airplanes, lawn equipment, etc.

How Do You Test a Magneto Coil with a Multimeter?

To check a magneto coil with a multimeter, follow these seven steps:

 

  1. Ensure there is no power running to the motor. 
  2. Remove the bolts and detach the shroud covering the flywheel. 
  3. Slowly pull off the spark plug’s rubber casing to reveal the coil’s unprotected copper windings.
  4. Set the multimeter to its Ohms setting and set it to the 40 k range (don’t use the auto-ranging feature).
  5. Place one tip of the probe on the engine block and the other on the rubber casing’s metal clip. 
  6. Ideally, the readout should be between 3 k and 15 k. If it’s higher than that, check the connection between the high voltage wire and the spark plug, then test again.
  7. If the multimeter reads O.L., the Magneto coil likely has a short.

Call Schott for Magnet Coil Testing

If you don’t have access to a multimeter or are having trouble figuring out how to check a magneto coil with a multimeter, call Schott Magnetics. Our 70+ years of experience with custom magnetics and contract manufacturing will serve you well!   

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