Electrical question..charging system..Sorry! (archive)

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My charging system failed last week. About 5 miles from home, each of my dash lights come on, one at a time, indicating failure of that system, starting with my SRS, then ATC, and so on. Upon ariving home, I killed it, then tried to restart. No dice, just clicking. Funny, I never saw the charging lamp come on, but my batteries were dead. I jumped it, and it fired right up, no dash lights, nothing. Until I disconnected the jumpers, then the lights on the dash came on again, then the engine died. Tried to start it again, just clicking.

I recharged my batteries over the next two days, then started over. First, before starting, 12.6 volts. After starting, 12.4 volts. Runs fine, no indicators of failure on the dash, but no output from the alternator.

Then, I did the test procedure of holding the odometer button down, while turning the key on. No charge lamp light. Next, with the key "on", my charging lamp does NOT light. When cranking, it does NOT light. After starting the engine, the lamp doesn't go out, because it never came on! I remember reading somewhere that the older BMWs wouldn't charge if the dash lamp was burned out. So, I pulled the instrument cluster to check/replace the bulb. It wasn't bad. I replaced it anyway, then reinstalled the dash. Still no lamp. Ever. With key on, in the start position, or in run.

I pulled the cluster again. This time I checked continuity on several lamp sockets, to compare to the charging lamp socket. All were open, except for the SRS (which checks fine), and the charging lamp socket. Both of these showed continuity across the lamp base. Why? I don't know.

I don't have (but wish I did) a schematic of the dash cluster VDO circuitry. I do know that I have continuity between BOTH sides of the charging lamp printed circuit and pin numbers 3, 5, 7 14, and 20, on the 26 pin main connector plug. Weird.

During checks on the cluster, volatage was never applied. Only continuity checks have been made.

Anyone know how the circuitry well enough to provide info? Or email me the schematic/s of the VDO Cluster?

I haven't convinced myself that the alternator, voltage regulator, or brushes have quit on me, since the dash lamp never lights up.

Additional info, 72,000 miles, I've only had this vehicle about 6 months, no trouble until now.

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