Lumenition MS4 Mega Spark 4 Ignition Coil – Supplied with Ballast Resistor

The Lumenition MS4 is an Optronic ignition system, identified as the Mega Spark 4 Coil and including a ballast resistor.

To check for a ballast resistor, use a voltmeter suitable for readings from 0–15 volts. Disconnect the lead or leads connected to the coil’s negative terminal. Use a suitable length of wire to connect the coil negative terminal to an earth point, then connect the voltmeter to the coil’s positive terminal.

Switch on the ignition and check the reading. If it remains at battery voltage, there is no ballast resistor in the circuit. If a ballast resistor is present, the reading will drop to approximately 9 V. Switch off the ignition immediately after the test. Do not leave the earth lead connected to the coil longer than required, as continued connection can overheat and damage the coil and drain the battery.