W205 C300 Alternator Idle Voltage Issue?
12-01-2022, 08:05 PM
#1
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Thread Starter
W205 C300 Alternator Idle Voltage Issue?
So recently i’ve been having a problem where my alternator won’t keep the voltage over 12.7 after i’ve started the vehicle; unless i rev the engine over 2K rpm or i drive the car over 2K rpm.
on two occasions i’ve forgot to rev the engine after i started the car while i’m idling, sleeping in my car and the battery ended up dying as a result.
yesterday,
i woke up out of my sleep in my car to all the electronics off, besides the heat. The cluster, center console, and COMMAND were all off. I tried turning OFF the car with my push to start button and the key- nothing. It was still on and the idle very weak, no misfire just a very weak idle..
Police came and tried to give me a jump, on the Vehicle Data screen my BN was at 0/100 which confirmed to me that the battery was dead dead. I tried starting it a minute after the cables made connection and it started, but weak again- systems and assistance features like blind spot and electric steering were unavailable.
after they tried charging me for about 10/15 mins the battery BN reached 7/100- which translated to about 10.7V they had to ‘leave for a call’ and i ordered an uber, which charged me a lil more for my car to start, once started i revved the engine for the voltage to keep over 12.7.. and went on a silent drive to charge the battery and think about what could possibly be the issue.
If it’s the alternator ok.. i’ve replaced it twice before because of the clutch that’s failed in the pulley.. but 3 alternators in 4 years is excessive- i believe?
Bought the car in
10/18/2018 with 53k miles,
i hit 140K miles 11/30/2022
maintained by myself
on two occasions i’ve forgot to rev the engine after i started the car while i’m idling, sleeping in my car and the battery ended up dying as a result.
yesterday,
i woke up out of my sleep in my car to all the electronics off, besides the heat. The cluster, center console, and COMMAND were all off. I tried turning OFF the car with my push to start button and the key- nothing. It was still on and the idle very weak, no misfire just a very weak idle..
Police came and tried to give me a jump, on the Vehicle Data screen my BN was at 0/100 which confirmed to me that the battery was dead dead. I tried starting it a minute after the cables made connection and it started, but weak again- systems and assistance features like blind spot and electric steering were unavailable.
after they tried charging me for about 10/15 mins the battery BN reached 7/100- which translated to about 10.7V they had to ‘leave for a call’ and i ordered an uber, which charged me a lil more for my car to start, once started i revved the engine for the voltage to keep over 12.7.. and went on a silent drive to charge the battery and think about what could possibly be the issue.
If it’s the alternator ok.. i’ve replaced it twice before because of the clutch that’s failed in the pulley.. but 3 alternators in 4 years is excessive- i believe?
Bought the car in
10/18/2018 with 53k miles,
i hit 140K miles 11/30/2022
maintained by myself
Last edited by am.gene; 12-01-2022 at 08:07 PM.
12-13-2022, 06:04 AM
#3
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12-13-2022, 10:47 AM
#4
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Join Date: Jan 2004
Location: Virginia
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17 E300, 17 C300, 14 C250
but 3 alternators in 4 years is excessive- i believe?
[/QUOTE]
I also went through 3 alternators in as many years - turns out the rebuilds I was buying from the big chain parts store were junk.
The rebuilt alternators from Bosch cost a lot more but were reliable (still less than from MB).
Lou
[/QUOTE]
I also went through 3 alternators in as many years - turns out the rebuilds I was buying from the big chain parts store were junk.
The rebuilt alternators from Bosch cost a lot more but were reliable (still less than from MB).
Lou
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Ron P Baker (12-13-2022)
12-15-2022, 05:03 AM
#5
Super Member
Since this is an electrical problem, it's hard to find an issue over the web. You need to do steps to find out the problem. First, did you get the alternator from Mercedes and did Mercedes install it? If you got it from Mercedes you have a 1 yr warranty on parts, if you didn't get it from Mercedes you will need to see what the warranty is, if there is one.
I would open the and see how the belts feel. They should be tight but not over tight but I don't think that is the problem. Keep in mine, a battery like the ones found in Start/Stop do not like to be discharged more than 3x. Anything after that and that battery is garbage but some people luck out but more don't.
You need find out if the alternator is charging properly since that is system to do just that to the battery.
I'm not sure why you had to change your alternator this many times unless you purchased cheap aftermarket parts.
I would open the and see how the belts feel. They should be tight but not over tight but I don't think that is the problem. Keep in mine, a battery like the ones found in Start/Stop do not like to be discharged more than 3x. Anything after that and that battery is garbage but some people luck out but more don't.
You need find out if the alternator is charging properly since that is system to do just that to the battery.
I'm not sure why you had to change your alternator this many times unless you purchased cheap aftermarket parts.
