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.
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HOMESERVICE MANUALSBMW1999328I 2D CONVERTIBLE, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ELECTRICALCHARGING SYSTEMSGENERATORS AND REGULATORSBENCH TESTINGROTORBOSCH
1999 BMW 328i 2D Convertible, Automatic
Bench Testing: Rotor: Bosch
1999 BMW 328i 2D Convertible, AutomaticSECTION Bosch
- Place DVOM on lowest scale. Connect DVOM across slip rings. Ensure resistance is within specification. See ROTOR RESISTANCE table.
- If resistance is too low, rotor has short circuit and must be replaced. If resistance is infinite (no continuity), rotor has an open circuit and must be replaced.
- Place DVOM on x1000 scale. Connect DVOM between rotor core and either slip ring. Continuity should not exist. If continuity exists, rotor is grounded and must be replaced.
- Measure slip rings for wear and eccentricity. If wear is visible, fine grind and polish slip rings. Maximum runout for slip rings is 0.11" (0.03 mm).
ROTOR RESISTANCE
| Application | Resistance (Ohms) | |
|---|---|---|
| Bosch | ||
| 65-Amp Generator | 3.2-3.6 | |
| 80-Amp Generator | 2.6-3.2 | |
| 90-Amp Generator | 2.7-3.2 | |
| 115-Amp Generator | 2.4-2.8 | |
| 140-Amp Generator | 2.4-2.8 | |
| Motorola | ||
| 65-Amp Generator | 3.5-4.5 | |
| 80-Amp Generator | 3.5-4.5 | |
RENDER: 1.0x
NO RELATED
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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.