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Ignition Parts 101: 3 Ways to Test the Coils March 8, 2017

Hilo, Hawaii
Ignition Parts 101: 3 Ways to Test the Coils, Hilo, Hawaii

The ignition coil in a vehicle converts 12 volts of battery power to thousands of volts that heat the spark plugs. It is made up of two ignition parts called coil windings, with one wire placed on top of the other. The primary winding uses battery voltage to make a spark. The other carries the spark to the vehicle’s distributor. If your vehicle fails to start, stalls frequently, or “misses” during acceleration, test the coils to see if either of the windings have failed.

3 Tests to Ensure Your Ignition Parts Are Running as They Should

Spark Plug Test

Refer to your vehicle manufacturer’s manual to remove the wire from the spark plug. Use insulated pliers to test the spark plug. Touch the threaded part of the plug to any piece of engine metal. Instruct a friend or family member to start the engine so you can check for a bright blue spark at the spark plug’s end. If the plug sparks a little, further testing is recommended. If no spark appears, the coil needs replacing.

ignition partsPrimary Winding Bench Test

Use this primary winding bench test if the plug emits a small spark only. Refer to the manual regarding your vehicle’s coil resistance specifications. The primary winding for most vehicles is between 0.75 to 0.81 ohm. Use a multimeter device to test the primary winding’s outside poles. Small, outside poles are featured on traditional ignition coils, while “indicated” poles are used on enclosed coil units. If the resulting reading is outside your vehicle’s resistance range, replace the coil.

Secondary Winding Bench Test

Look up the recommended resistance range for your secondary winding, which is usually between 10,000 and 11,000 ohms. Attach your multimeter to the secondary winding’s center pole and outer 12V pole. Use your manual to determine which pole is the 12V terminal. Again, if the winding is out of the recommended resistance range, coil replacement is necessary.


Work with the experienced, knowledgeable team at Automotive Supply Center to keep your ignition parts in great condition. The family-owned purveyor of automotive parts has provided the Hilo, HI, area with an outstanding inventory since 1956. Contact them at (808) 935-3767 or visit their website to learn what they have available. Like the company on Facebook for more vehicle maintenance tips.

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