Installing a Flyback/Clamping Diode

Inductive loads like a solenoid create a reverse voltage spike of several hundred volts when power to the solenoid is switched off. This high voltage may cause damage to sensitive electronic circuits so it is best practice to suppress the voltage spike right at the load using a resistor or a diode connected in reverse polarity. The diode will shunt the reverse voltage and prevent it from causing damage.

The example below demonstrates connecting our  epoxy encapsulated diode package across the coil of a fuel solenoid on an engine.

1. Stop the engine, and disconnect the battery ground cable.
2. Remove the two terminal nuts from the Injection Pump Solenoid. Leave existing wires in place.
3. Connect the Diode Package red wire to the  Positive + terminal of the solenoid.
4. Connect the Diode Package black wire to the Negative – terminal of the solenoid.
5. Replace the terminal nuts and tighten securely.
6. Reconnect the battery ground cable

Download this article as a PDF (IDHP-98067N / 00-02-0317)
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