Electrical Gremlins
Thread Starter
Newbie
Joined: Dec 2020
Posts: 5
Likes: 4
2011 C63
Electrical Gremlins
Hi there, reaching out as I'm at a standstill with my 2011 C63.
120XXX kms on the odometer
So in the past month or so my battery light is coming on quite regularly. I replaced the battery and it disappeared. Bought a battery locally and as far as the specs were concerned it exceeded OEM for about 250$
Now a few weeks later battery light came on again and so I replaced the alternator. All seemed good for a day or two and now the battery light is back.
I watch my voltage on my display as I drive and on startup I hover at 12.3-12.4 and over the span of 15 minutes ill dip below 11.8. Once I shut the car off and I turn it back on it starts to charge over the span of another 15 minutes or so ill see it reach 13.2 - 13.3 (Maybe higher my drives just generally aren't that long)
I tried to charge my battery to full to see if that may rectify the issue. No dice it never charges on a cold start. I took a peak at my connector on the alternator thinking maybe that was an issue and seen no problems but cleaned it anyway. The only thing I did notice is that the alternator has 2 pins but I only have 1 wire going to it (plus the main)
Any help would be greatly appreciated.
120XXX kms on the odometer
So in the past month or so my battery light is coming on quite regularly. I replaced the battery and it disappeared. Bought a battery locally and as far as the specs were concerned it exceeded OEM for about 250$
Now a few weeks later battery light came on again and so I replaced the alternator. All seemed good for a day or two and now the battery light is back.
I watch my voltage on my display as I drive and on startup I hover at 12.3-12.4 and over the span of 15 minutes ill dip below 11.8. Once I shut the car off and I turn it back on it starts to charge over the span of another 15 minutes or so ill see it reach 13.2 - 13.3 (Maybe higher my drives just generally aren't that long)
I tried to charge my battery to full to see if that may rectify the issue. No dice it never charges on a cold start. I took a peak at my connector on the alternator thinking maybe that was an issue and seen no problems but cleaned it anyway. The only thing I did notice is that the alternator has 2 pins but I only have 1 wire going to it (plus the main)
Any help would be greatly appreciated.
Thread Starter
Newbie
Joined: Dec 2020
Posts: 5
Likes: 4
2011 C63
Hopefully someone will chime in here, swapped the alternator for a tested "good one" and had the car on my lift and tested the voltage directly from the alternator and was at 14.6-14.8 volts steady.
Threw in a battery from my truck (lead acid not agm) to see if maybe that would change my readings but still only 12.1-12.4 volts at the battery.
Starting to think circuitry somewhere is wrong, any relays or electrical components associated with the charging system that may cause this?
Any help ladies and gents!
Threw in a battery from my truck (lead acid not agm) to see if maybe that would change my readings but still only 12.1-12.4 volts at the battery.
Starting to think circuitry somewhere is wrong, any relays or electrical components associated with the charging system that may cause this?
Any help ladies and gents!
Thread Starter
Newbie
Joined: Dec 2020
Posts: 5
Likes: 4
2011 C63
In the event that anyone has the same issue. I did rectify the issue. Was as simple as corrosion under the bolt head of the engine to chassis ground.... (location on gearbox) was as simple as testing alternator to chassis voltage vs alternator to engine voltage!
Junior Member
Joined: May 2023
Posts: 16
Likes: 1
2014 C63 507
Hi - Where was this ground located? I’m having the same issues, new battery new alternator (reman) and a couple days later my battery light is back and I’m lost now lol
