Question: How do I test a generator / stator?
Answer:
You can largely test a generator (stator) yourself with a multimeter. The exact values differ per model — consult the workshop manual where possible.
1. Visual inspection
Burnt or discoloured windings, melted insulation or a burnt smell almost always indicate a defective stator.
2. Static measurement (engine off, connector disconnected)
• Measure the resistance between the phase wires. All combinations should give a nearly identical, low value (often between 0.1 and 1.5 ohms, depending on the model).
• Measure between each phase wire and the engine block (ground): there must be no continuity. Any connection to ground means the stator is defective.
3. Dynamic measurement (engine running, connector to the regulator disconnected)
Measure the AC voltage between the phase wires. All combinations should give a nearly identical voltage that clearly increases with engine speed. One deviating phase means the stator is defective.
Please note: a stator can measure fine and still be defective. Short circuits between the windings often only show up when the stator is hot or under load. In doubt, or do you want certainty? Send the stator (preferably together with the regulator/rectifier) in for diagnosis — we test under load. See the FAQ "How do I send in my part for testing or repair?".
