Generator & Regulator: Diagnosis BMW 3 series E46

TROUBLE SHOOTING

Note. See TROUBLE SHOOTING - BASIC PROCEDURES article in the GENERAL TROUBLE SHOOTING section.

WIRING CONTINUITY TEST

1. Connect voltmeter between generator B+ terminal and ground. Voltmeter should indicate battery voltage. If battery voltage is not indicated, check wiring between generator and battery.
2. Turn ignition on and ensure generator indicator light comes on. If light does not come on, check indicator light bulb and wiring between generator and warning light.

OUTPUT TEST

1. Ensure connections at battery, generator, and starter are clean and tight. Ensure generator, engine and body are properly grounded.
2. Ensure generator drive belt is tight and in good condition. Connect charging system tester according to manufacturer's instructions. Connect voltmeter leads to battery terminals.
3. Start and operate engine at 3000 RPM. Adjust carbon pile on tester to obtain maximum generator output. DO NOT allow voltage to drop to less than 12.6 volts.
4. Generator output should equal generator rated output. If reading is 16-20 amps less than generator rating, replace regulator and retest. If output is still low, repair or replace generator.

REGULATOR CONTROL VOLTAGE TEST

1. Connect charging system tester according to manufacturer's instructions. Connect voltmeter leads to battery terminals. Start and operate engine at 3000 RPM.
2. Operate engine until voltage stops rising. Voltage should be 13.5-14.2 volts. If reading is incorrect, remove regulator and ensure brushes are longer than 0.198" (5.0 mm). Replace if necessary.
3. If brushes are okay and regulator fails to keep voltage within specified limits, replace regulator and retest. If voltage is still incorrect, repair or replace generator.