I'm in trouble
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1990 300E
I'm in trouble
This morning on my way to school my car was running funny and it sounded like it had a vacuum leak. Leaving school this afternoon everything was fine until my ABS and SRS warning lights came on. Then the radio went, followed by the windows and HVAC. Finally the car started running poorly and died. I thought perhaps i blew a fuse and there was a burnt out fuse so i replaced it. i was able to start the car again after that but i stalled out again. I was not able to get it started for another 20 or so min. The fuse that i replaced was fine. Please help me. Thanks
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From: Massachusetts
2018 GLE350, 2014 G550, 2000 SL500, 1980 TR8, 1995 E320 Cabriolet
It does indeed sound like a charging problem. The SRS and ABS modules both monitor the system voltage (right from the alternator field circuit) so they are often the first to come on in the event of a low voltage situation - the proverbial canary in a coal mine, if you will.
The most likely source of a charging problem is the voltage regulator/brush assembly. This is an easy R&R with the alternator on the car. I would check the system voltage with the car running - anything less than about 12.8 volts and it is probably not charging. I would also do this quick test - turn the key all the way to the "run" position, but don't star the car. You should get the "lamp check" where all the instrument cluster lamps come on so you can verify they are working (okay, who actually does that). Excluding the Check Engine light (if equipped), the ABS, and the SRS lights, if the rest do not illuminate, the brushes in the alternator (part of the voltage regulator assembly) are bad.
Good luck,
- FD
The most likely source of a charging problem is the voltage regulator/brush assembly. This is an easy R&R with the alternator on the car. I would check the system voltage with the car running - anything less than about 12.8 volts and it is probably not charging. I would also do this quick test - turn the key all the way to the "run" position, but don't star the car. You should get the "lamp check" where all the instrument cluster lamps come on so you can verify they are working (okay, who actually does that). Excluding the Check Engine light (if equipped), the ABS, and the SRS lights, if the rest do not illuminate, the brushes in the alternator (part of the voltage regulator assembly) are bad.
Good luck,
- FD
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From: Massachusetts
2018 GLE350, 2014 G550, 2000 SL500, 1980 TR8, 1995 E320 Cabriolet
16 volts is too high if your meter is accurate. A variation over a large range like 13 - 16 tends to further point to a failing VR or perhaps a failing battery (internal intermittent causing to to go "open" under load).
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From: Massachusetts
2018 GLE350, 2014 G550, 2000 SL500, 1980 TR8, 1995 E320 Cabriolet
When the car wouldn't start for another 20 or so minutes, did it fail to crank over or did it crank over, but not start?
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MBWorld Fanatic!
Joined: Nov 2002
Posts: 1,028
Likes: 133
From: Massachusetts
2018 GLE350, 2014 G550, 2000 SL500, 1980 TR8, 1995 E320 Cabriolet
Okay, that is most consistent with a failing VR. The car runs until the decreasing battery voltage causes a loss of spark or fuel pressure so it dies. Lead acid batteries exhibit some "self recovery" if let sit for a while (a la, 20 minutes), so the car could then be started.
