SL/R230: Starting & running issue
Thread Starter
Junior Member
Joined: Jan 2018
Posts: 17
Likes: 1
From: Calgary, AB
2007 SL550
Starting & running issue
I have a 2007 SL550. A few days ago the red battery notice appeared on my instrument panel and then went out. I have had no issues starting or driving. Yesterday when I started it, the engine sounded like a diesel (rattle) for a minute. After the engine sounded normal ( maybe a minute) I started to drive only to have the car engine completely stop and all of the warning symbols appeared in the cluster. After stopping the car, I tried to start it however, even though it turned over very strong it would not start. Once the vehicle was towed back home, I tried to start it again only to have the engine once again sounding like a diesel (without starting) and then a backfire. There is a terrible ratel sound from the engine and another backfire.
Does anyone have any suggestions or do I have it towed to the dealership?
Any advice is greatly appreciated.
Does anyone have any suggestions or do I have it towed to the dealership?
Any advice is greatly appreciated.
Senior Member
Joined: Jan 2015
Posts: 390
Likes: 115
From: Seattle, WA
SL500 & GL450
Your alternator (more specifically, the voltage regulator on your alternator) could be failing.. This would explain the brief red battery light, as well as the rough running and stalling. When the voltage regulator is failing, you are intermitently running on battery alone as the alternator isn't providing a voltage level high enough to both charge the battery, and provide consistent high voltage spark to the spark plugs. Eventually the battery will get low enough that it can't provide enough high voltage juice at all, and then the engine will shut off. With your symptoms, that would be my starting point. Luckily the voltage regulator is an easy/cheap replacement (Just 2 screws where the wire harness plugs into the alternator). Alternatively, a new alternator can be purchased and it'll come with a new voltage regulator already installed.
Thread Starter
Junior Member
Joined: Jan 2018
Posts: 17
Likes: 1
From: Calgary, AB
2007 SL550
Your alternator (more specifically, the voltage regulator on your alternator) could be failing.. This would explain the brief red battery light, as well as the rough running and stalling. When the voltage regulator is failing, you are intermitently running on battery alone as the alternator isn't providing a voltage level high enough to both charge the battery, and provide consistent high voltage spark to the spark plugs. Eventually the battery will get low enough that it can't provide enough high voltage juice at all, and then the engine will shut off. With your symptoms, that would be my starting point. Luckily the voltage regulator is an easy/cheap replacement (Just 2 screws where the wire harness plugs into the alternator). Alternatively, a new alternator can be purchased and it'll come with a new voltage regulator already installed.
