ESI Direct Voltage Adapter
For DIY types, troubleshooting capacitor discharge ignitions (CDI) require a familiarity with the components, the correct service literature, and proper test equipment. These expensive and unique specialty tools are often unaffordable for the home mechanic who is attempting to repair his motor. Service manuals require the use of a direct reading voltmeter or a DVA adapter to measure the outputs from charge-coils, ignition modules, and pulser or trigger coils. Ordinary digital meters cannot accurately test the short-duration peak voltages at the high frequencies generated by CDI components.
Electronic Specialties, Inc. offers a $39 retail DVA adapter that plugs into a digital multi-meter for checking CDI output voltages. The #640 DVA tester consists of a small module equipped with dual banana clips that are inserted into the + & – jacks of a digital multi-meter (DMM). In addition to the banana clips, the module has two test leads with both probes and alligator clips for testing the various types of ignition components.
Capacitor discharge systems produce alternating current (AC) and pulsing direct current (DC). A stator charge-coil has an AC output while pulsing DC voltages are measured on an ignition module or trigger. Most AC meters are made for 60 Hertz electrical voltages and are not designed to read the high frequencies encountered with an outboard motor.
DC digital meters cannot accurately read a pulsing DC voltage. To illustrate this, connect a digital meter to a 12 volt battery and rapidly tap one of the probes against a terminal and read the voltage. The slower you tap, the lower the voltage reading. As you tap faster the reading approaches the battery voltage. A peak reading voltmeter is designed to “hold” the readings between the DC pulses, and to indicate the difference between the positive and the negative peaks of an AC voltage.
The ESI #640 DVA adapter is plugged into a digital meter and the voltage range is normally set to about 400V DC for most testing. Trigger, pulser, and timer-base outputs use a lower voltage range. Generally, the test leads are attached to the component and the engine is cranked over while the output voltage is displayed on the meter.