1991 Mercedes Benz 300e Not charging, (almost) no warning l

SHANUU

MEMBER
1991 MERCEDES BENZ 300E

Electrical problem
1991 Mercedes Benz 300e 6 cyl Two Wheel Drive Automatic

Hi. I was driving down the road the other day, stopped my car for a few minutes, and when I started it again I sensed something was wrong; it didn't charge, but the battery lamp wasn't lit up(no warning lamps was).

I turned off all electricity and managed to get home and turned of the car. It was of course not enough power left on the battery to start it again, so I used jumper cables. The strange thing was that when I turned the key, right before the engine starts when all the warning lights are supposed to be lit, only the ABS-light was lit? I'm wondering if this has something to to with the car not charging? (The ABS light went dark again when the engine started, I have and have never had any problems with the ABS, but this lamp was the only one acting "normally").

I will measure the voltage drop over the battery and the alternator, and check if the wire to/from the battery warning lamp is ok, but I suspect the mistake might be something else, like the control unit?

Anyone have any ideas, and know how to rfind out what's wrong?

1 Reply

TDHC13

MEMBER
3 POSTS

Attach voltmeter to your positive battery cable when the car is running and measure voltage. It should read anywhere between 13 and 14 volts with the car running and a good alternator. 12 volts or less with the car running indicates a "charging" problem. If you have an DC ampmeter, measure amperage coming off the battery terminal at the alternator with the car running. This will tell you for sure whether the alternator is puttiing out power. The alternator amperage will depend on the load that you are requiring from it. The greater the demand the more amperage the alternator is designed to deliver, up to its maximum capacity, usually 80-100 amps. Be sure to check for broken or loose battery cables at the battery and on the power cable to the alternator and be sure belt to alternator pulley is not loose or broken. Actually, this inspection should be the first step. Also be sure that battery is good. Hope this helps.