Charging System - Possible Insufficient Charge, Testing

Group 12
Engine - Electric



Bulletin Number
12 11 88 (1760)



Woodcliff Lake, NJ
February 1989
Technical Dept.



This Service Information Bulletin supercedes S.I. 12 11 88 (1760) dated January 1989. The Parts Ordering Procedure has been changed to allow normal parts ordering directly from the PDC'S.

Please remove and discard S.I. 12 11 88 (1760) dated January 1989 from your S.I. binder.

SUBJECT:
Overall Charging Condition

MODEL:
E32

Situation:
Under certain driving conditions (city; stop and go), particularly during the winter months, it is possible that the battery may not receive a sufficient charge. As a result, the engine may not restart when turned OFF.

Beginning with the 1989 models several items have been changed to correct this situation:

735i/735iL --- 140A alternator (instead of 115A)

750iL --- Smaller alternator pulley (higher ratio for more
revolutions per engine revolution)

All --- Passenger seat heating -- seatbelt must be fastened to operate

Older vehicles driven under these conditions can also be improved with the alternator modifications:

735i/735iL --- Install 140A alternator;
--- Install smaller alternator pulley.

750iL --- Install smaller alternator pulley.

These items are only to be performed in conjunction with a complete check of the battery and charging system.



Repair Procedure:





STEP 1 -- BATTERY LOAD TEST
Using a Sun VAT-40 (or equivalent) Charging System Tester, load test the battery for 15 seconds at the appropriate amperage listed (electrolyte temperature minimum 65~F):

735iAL 84 Ah battery = 340A

750iL 85 Ah battery = 371A



STEP 2 --- ALTERNATOR MODIFICATION

735i/735iL -- following the procedure in the Workshop Manual, replace the alternator with a 140A alternator P/N 12 31 1 717 395. Also install a smaller alternator pulley P/N 12 31 1 722 983 (torque pulley nut to 36 ft.lb.).

750iL -- replace the existing alternator pulley (54 mm) with a smaller pulley (46 mm) P/N 12 31 1 720 368 and new fan wheel P/N 12 31 1 725 734 (torque pulley nut to 36 ft.lb.).

Note:
To gain access to the alternator pulley, remove the engine cooling fan and fan shroud.


STEP 3 -- CHARGING SYSTEM CHECK Check alternator output at the battery by applying a load using a Sun VAT-40 (or equivalent) Charging System Tester.

With all electrical components turned OFF, run the engine at 3000 rpm. Increase the load until the voltage reading is 12.0 volts. The amperage output should be at least 120 amps.

If not, check the battery cables for proper connections following the procedures in S.I. 61 64 88 (1619).



STEP 4 - PARASITIC DRAW TEST With all electrical consumers turned OFF (car unlocked, key out of ignition) the maximum draw on the battery should not exceed 0.050A.

Using a hand held multimeter check the parasitic load as follows:

^ Connect one lead to the negative battery post.

^ Connect the other lead to a known good ground point on the body.

^ Open right rear (RR) window and close all doors.

^ Disconnect negative battery cable at connection located on the front of the RR seat.

^ If draw exceeds 0.050A, locate source of excessive draw and repair.

Warranty Status:





Covered under the terms of the BMW New Car Limited Warranty of 3 Years/36,000 Miles.