Voltage issues
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Joined: Jun 2018
Posts: 1
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2003 W211 E500
Voltage issues
Hey guys, lurked this forum for years now, finally made an account.
Long story short, about 5 months ago, I was driving, my brakes made a loud screeching noise, then popped up on the dash was "Brake Malfunction, stop vehicle." and then my brakes barely did anything. I was then having electrical issues, I just didn't have the time to try and fix anything that was wrong with it and it also occurred in the winter so it was too cold to work on it. After some self-diagnosis, in the past week I've replaced the voltage regulator, the rear main battery, and the CPS. After replacing the main battery and fully recharging the auxiliary battery, the car started better than ever and actually drove a 20 mile distance before right when I arrived at my friends house (where I was dropping it off) it threw up the "Battery/Alternator" red warning along with BRAKE MALFUNCTION, and so I hooked up my main and Aux. battery to the trickle charger I have and found that the Aux battery is at around 13.7V and my main battery dropped from 12.9 to 11.8. While the car still started again and multiple times, it will stay at a constant voltage around 11.8-11.5 while slowly decreasing.
I'm curious as to what you guys think it could be, I just ordered a used alternator today and plan on replacing it as I suspect that it's barely supplying power, although if that fails then I suspect it is the BCM, although i'm not sure which one.
thoughts? Thanks!
Long story short, about 5 months ago, I was driving, my brakes made a loud screeching noise, then popped up on the dash was "Brake Malfunction, stop vehicle." and then my brakes barely did anything. I was then having electrical issues, I just didn't have the time to try and fix anything that was wrong with it and it also occurred in the winter so it was too cold to work on it. After some self-diagnosis, in the past week I've replaced the voltage regulator, the rear main battery, and the CPS. After replacing the main battery and fully recharging the auxiliary battery, the car started better than ever and actually drove a 20 mile distance before right when I arrived at my friends house (where I was dropping it off) it threw up the "Battery/Alternator" red warning along with BRAKE MALFUNCTION, and so I hooked up my main and Aux. battery to the trickle charger I have and found that the Aux battery is at around 13.7V and my main battery dropped from 12.9 to 11.8. While the car still started again and multiple times, it will stay at a constant voltage around 11.8-11.5 while slowly decreasing.
I'm curious as to what you guys think it could be, I just ordered a used alternator today and plan on replacing it as I suspect that it's barely supplying power, although if that fails then I suspect it is the BCM, although i'm not sure which one.
thoughts? Thanks!
MBWorld Fanatic!
Joined: Jan 2009
Posts: 9,225
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From: V E G A S
1922 Ford Model T / no OBD
You have multiple issues and let's hope the brake error is due to low voltage.
So new main battery is loosing the voltage.
That means it is not getting charged. With new VR the control module would be next suspect.
Fill up your profile with car MY and tell us what scanning can you do?
So new main battery is loosing the voltage.
That means it is not getting charged. With new VR the control module would be next suspect.
Fill up your profile with car MY and tell us what scanning can you do?
