How can I test the electrical system on my John Deere?
To test your electrical system on your equipment, inspect battery voltage, ignition switch continuity, fuses, and wiring.
If your engine won’t start and you’ve ruled out the battery, the issue may lie deeper in the electrical system. Begin by testing the battery with a multimeter to ensure it reads at least 12.6 volts when fully charged. Then, inspect all visible wires for wear, corrosion, rodent damage, or loose connections, especially around the starter, solenoid, and ignition switch.
Next, check all fuses and relays. A blown fuse or faulty relay can interrupt power to the fuel solenoid, ignition system, or starter motor. Use a test light or multimeter to verify power is flowing through each fuse and relay when the key is turned.
Then, test the ignition switch for continuity in the “Start” and “Run” positions. Over time, switches can corrode internally, causing intermittent or failed starting. Make sure all safety switches (seat, brake, PTO) are also functioning. These are often wired in series, meaning one failed switch can stop the entire circuit.
If needed, consult the wiring diagram for your specific John Deere model and trace voltage from the battery to the starter to pinpoint the break or fault in the circuit.
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