generator not charging

[ricky9089]

1965 230sl.
the reason i believe the alternator is not charging is becouse the battery keeps going dead. I did notice the gen. light on the dash does not come on at an given time niether the low brake or door ajar light come on. Not sure if the brake and gen. light have any thing in common. any suggestion where to start. aslo check batt. v. while cars was idling v. reamaind at batt. v. never went above 13v.

[star63]

I would start from the voltage regulator...

[Rolf-Dieter ✝︎]

I had the same issue with my daughters BMW  535is 1987 (was my first new BMW and she will never sell it). Anyway I charged her battery in the hope to get the car to the station. All was fine and after about 2 miles the car went dead hat to be towed to the shop. Result required a new alternator. The old one would no longer charge the battery.

[garymand]

New Alternator?   battery keeps going dead?  So I think you are saying you can charge the battery with a battery charger and start the car with that battery.  AND, you measured less that 13 volts at the batery with the motor running.

If so the battery is not likely the problem.   Start the motor.  Measure the voltage at the battery.  If the charging is good you will see over 13 volts.  If no charging 12 to 12.5 depending on charge on the battery. 

The brush assembly is held in with 2 screws and is easily replaced.  Not sure what you are describing as syptoms.  Not sure how many brushes you can go through on these, but I'm on my 3rd.   Brushes are cheap, alternators are not.

 If you have 60 to 100K on the alternator, for sure replace the brushes, but yes it could be the regulator has failed first.  Take it to an automotive parts store, most troubleshoot the charging system for free at least around here.

[ricky9089]

just an update, had the alteernator tested and turnd out to be good. the problem was the aliternator bulb in the dash board was burnt out. So i replaced all the bulbs and the charging system is working the way it should putting out above 14 v.

[ja17]

Rare circumstance since the bulb is only on for short periods. Yes, the alternator field is energized from a hot circuit which travels through the charging light. You may want to have a volt meter check on your charging system to make sure that the voltage is not too high. High voltages cause premature burnout of light bulbs.