SL/R230: Battery light on
Thread Starter
Junior Member
Joined: Mar 2020
Posts: 15
Likes: 0
2004 SL55 AMG
Battery light on
This is what iv done so far. New starter battery checked fuse in passenger foot well still have the red battery light on.
the battery in the back is good as when I check it I'm getting 13.8v and 14.2v with the engine running so I know it charging but why am I only getting 12.5 on the starter battery when it running
Any help would be great thank.
the battery in the back is good as when I check it I'm getting 13.8v and 14.2v with the engine running so I know it charging but why am I only getting 12.5 on the starter battery when it running
Any help would be great thank.
Super Member
Joined: Jul 2014
Posts: 992
Likes: 245
From: Tucson, AZ
'20 X5 M50i; '17 Ram 3500; Golf Cart; Bikes; Scooters
Your voltage sounds good, and this error is normally a charging or voltage issue.
'm going to take a stab at this and ask if you disconnected the rear battery before replacing the front starter battery?
The car wants the rear disconnected first, then the front disconnected.
Connect the front first, then the rear when hooking up cables.
Go try this and see what happens.
'm going to take a stab at this and ask if you disconnected the rear battery before replacing the front starter battery?
The car wants the rear disconnected first, then the front disconnected.
Connect the front first, then the rear when hooking up cables.
Go try this and see what happens.
Thread Starter
Junior Member
Joined: Mar 2020
Posts: 15
Likes: 0
2004 SL55 AMG
Yeah I did that just the negative lead off the consumer battery and then removed the old starter battery, installed new starter battery and recontected the negative lead back on the consumers battery was think that if the bcm was bad then the consumers battery would not charge am i right in thinking that
Banned
Joined: Feb 2014
Posts: 276
Likes: 33
SL500, Miata
You could play Parts Roulette with some relays, since they can cause a "red fault" as well. But why not spend $135 on a Foxwell device or $250 on Star Diagnosis and read the code which is causing the fault indication?
Super Member
Joined: Jul 2014
Posts: 992
Likes: 245
From: Tucson, AZ
'20 X5 M50i; '17 Ram 3500; Golf Cart; Bikes; Scooters
^^^...this is the next step if the battery disconnect does not work. If you DIY, you MUST have a Star for this car. It has saved me, and all my MB friends, thousands of dollars PER YEAR.
