Tech Tip: Mercedes-Benz Alternator/Generator Voltage Regulator Malfunction
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Tech Tip: Mercedes-Benz Alternator/Generator Voltage Regulator Malfunction

On some Mercedes-Benz vehicles, if you encounter insufficient alternator/generator (G2) output, the voltage regulator, integral to G2 output, may be malfunctioning. The voltage regulator may be replaced as a separate part and the procedure in this Tech Tip should be followed.

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Affected vehicles: All model 203, 209, 211, 215, 220 and 230 with M112/113 engine, all model years

On the above model vehicles, if you encounter insufficient alternator/generator (G2) output, the voltage regulator, integral to G2 output, may be malfunctioning. The voltage regulator may be replaced as a separate part and the procedure below should be followed.

1. Check regulation voltage of the generator (G2) as per WIS instructions:

– Model 203/209: AR15.40-P-5010P
– Model 211: AR15.40-P-5010T
– Model 215/220: AR15.40-P-5010I
– Model 230: AR15.40-P-5010R.

2. If the generator fails the above test procedure, then remove the unit from the vehicle for repair on a workbench. Refer to WIS Group 15.40 for the correct instructions, depending on the model and body variant. fig. 1

3. Remove the plastic cover from the rear of the generator, by first removing the two nuts from the studs (Fig. 1, 1) and the one Philips head screw (Fig. 1, 2). Note which nut is removed from either stud.

4. Remove the voltage regulator (Fig. 2, 1) from the generator, by removing the three Philips head screws (Fig. 2, 2 and 3). fig. 2

5. Check the following prerequisites to ensure that only the regulator needs to be exchanged. If any of the following items fail, then the entire generator needs to be replaced and you may proceed to step 8.

a. There are no scorch marks or damage on the slip ring of the generator rotor (Fig. 3, 1).fig. 3

b. The carbon brush length of the defective regulator is at least 5 mm (Fig. 4, 1).

c. The wear on the two brushes of the defective regulator is even (maximum 1 mm difference).

6. Install the new voltage regulator and tighten the Philips head screws to: Fig. 4

a. Fig. 2, 2 = 2.0-2.4 Nm.
b. Fig. 2, 3 = 1.0-1.4 Nm.

7. Install the plastic cover on the back of the generator and tighten the Philips head screw (Fig. 1, 2) to 2.2-2.6 Nm and the two nuts (Fig. 1, 1) as follows:

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a. Long stud to 29.0-32.0 Nm.
b. Short stud to 11.0-13.0 Nm.

8. Reinstall the repaired generator or the new generator in reverse order and verify proper operation as described in step 1.

Note: Due to the several versions of alternator/generators used in production on all the above models, please refer to EPC for the correct voltage regulator part number application. The correct part numbers may be found in group 15 and/or 54 in EPC.

Courtesy of Identifix.

 

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