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.
Rotor Test
Test rotor for grounded, open or shorted field coils using an ohmmeter. Test for grounds between slip rings and rotor shaft; no continuity should exist. Check for an open field by connecting ohmmeter across slip rings, 1.7-2.1 ohms (100 amp.) or 1.5-2.0 ohms (all others) is normal resistance with rotor at room temperature. Readings above 3.5 ohms indicate high resistance and rotor replacement may be necessary. If reading is 1.7 ohms (100 amp.) or 1.5 ohms (all others) or less, the field coil is shorted.
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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.