Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Electrical System Diagnosis
Perform this diagnostic procedure if engine does not start when cold. "GLOW PLUGS" light may or may not come on. Check fuel system to ensure it is okay. Ensure battery voltage is 12.4 volts or more with ignition switch off. Check that cranking speed is at least 100 RPM.
- Connect 12-volt test light to ground. Place test light lead on battery stud (single Red wire) on controller. If test light does not glow, repair open circuit between battery and controller.
- If test light glows, place test light lead on glow plug feed stud (2 Orange or Red wires) on controller. If test light glows, relay contacts are shorted. Replace controller and all glow plugs.
- If test light does not glow, disconnect harness from all glow plugs. Connect test light to battery (12-volt source) and touch each glow plug terminal. Test light should glow. Replace glow plug(s) if light does not glow.
- Connect all glow plugs. With ignition switch in "RUN" position, connect 12-volt test light to ground. Remove controller connector and check voltage (from ignition switch) at terminal "D" of harness connector.
- If test light does not glow, repair open circuit from ignition switch to controller. If test light glows, connect test light to battery (12-volt source) and check for ground at terminal "E" of harness connector.
- If test light does not glow, repair open in ground wire to terminal "E" of connector. If test light glows, connect test light to battery (12-volt source) and check terminal "C" of harness connector. If test light glows, replace glow plug controller.
- If test light does not glow, remove temperature inhibit switch connector and check for continuity through switch. Switch should be open above 125°F (52°C).
- If continuity exists, repair open circuit in harness between glow plugs and terminal "C" of harness connector. If no continuity exists, replace inhibit switch.
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.