How to Test a 12-Volt Condenser

by Dwight Chestnut

A 12-volt condenser is part of an automotive ignition system. The battery provides power to the primary side of the ignition coil, which in turn produces high voltages across the secondary windings of the ignition coil. The voltage from the secondary winding is fed to the spark plugs as required to start the engine. The purpose of the condenser is to protect this ignition system from stray voltages that can interfere with the efficiency of the ignition coil. It does this by functioning as an insulator between the stray voltages and the ignition system.


Put on electrical safety gloves as part of the safety precaution necessary to protect yourself from electrical shock.


Disconnect and remove the condenser from the associated circuitry. Ensure the condenser and all parts are dry since dampness may cause misleading results.


Connect a megger across the condenser terminals. The megger will produce a high voltage as required to measure resistance of the condenser in megohms. Put the positive lead of the megger on the positive terminal of the condenser and the negative or ground end of the megger to the negative terminal of the condenser.


Start up the megger. Select the 500-volt range using the voltage range dial on the megger. Be sure you are not touching the condenser while doing this step. You should get an initial reading of 10 megohms or more on the megohm meter located on the front panel of the megger. Within a few seconds, the resistance should increase to several hundred megohms as the condenser charges up. You should quickly obtain a stable resistance of infinity or at the highest level of the megohm meter. This high resistance will validate the condenser is functioning as an insulator because an insulator has infinite resistance. If the initial reading is less than 10 megohms or if the resistance doesn't increase significantly within a few seconds, this means the insulation in the condenser is failing and the condenser needs to be replaced.

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About the Author

Dwight Chestnut has been a freelance business researcher and article writer for over 18 years. He has published several business articles online and written several business ebooks. Chestnut holds a bachelor's degree in electrical engineering from the University of Mississippi (1980) and a Master of Business Administration from University of Phoenix (2004).

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