SL/R230: Replaced Alternator
Thread Starter
MBworld Guru
Joined: Dec 2009
Posts: 10,782
Likes: 1,011
NO LONGER ACTIVE
Replaced Alternator
I've noticed lately that my hardwired Escot radar detector would shut off right after starting with a "low voltage" message. I figure my consumer battery was either not getting enough of a charge or was on its way out. I think, though that my alternator has been slowly dying. Yesterday, I got the red battery icon and eventually a "low voltage - stop engine" message. It was down to 10.8v. I charged the battery overnight, and the alternator was putting out 14v this morning, but later in the day, with the engine hot, it dropped down below 11v again.
I scanned the BCN and other systems and found nothing wrong besides the low voltage. I could also see that then the voltage dropped below about 106. the BCN was switching to the starter battery as voltage would temporarily jump back up over 12v. So, I decided to swap the alternator. Advance Auto had a lifetime warranty rebuilt in stock foe about $200, then 15% off for ordering online with store pickup.
The job took about two hours. I know I've mentioned this before, but the Craftsman Universal Max Axess socket set is a must-have. I don't think I could have gotten to the bolts any other way. The biggest challenge was working alone, trying to hold the alternator against the block while getting bolts started. Also, in case anyone wants to know, it comes out from above, after removing the air pump injection valve and the right exhaust camshaft position sensor.
I took a drive around the neighborhood and all seems well. I'll get out and drive some more tomorrow to see if it keeps working when it gets hot.
I scanned the BCN and other systems and found nothing wrong besides the low voltage. I could also see that then the voltage dropped below about 106. the BCN was switching to the starter battery as voltage would temporarily jump back up over 12v. So, I decided to swap the alternator. Advance Auto had a lifetime warranty rebuilt in stock foe about $200, then 15% off for ordering online with store pickup.
The job took about two hours. I know I've mentioned this before, but the Craftsman Universal Max Axess socket set is a must-have. I don't think I could have gotten to the bolts any other way. The biggest challenge was working alone, trying to hold the alternator against the block while getting bolts started. Also, in case anyone wants to know, it comes out from above, after removing the air pump injection valve and the right exhaust camshaft position sensor.
I took a drive around the neighborhood and all seems well. I'll get out and drive some more tomorrow to see if it keeps working when it gets hot.
Junior Member
Joined: Nov 2014
Posts: 58
Likes: 11
2003 SL500
Hi Rod,
I did the voltage regulator switch on my 2003, and stabilized the alternator output. I compared the old brushes to new, and they were worn about 50%. So far, so good, but I'm sure a new alternator would be more peace of mind. Thanks for all your informative posts.
I did the voltage regulator switch on my 2003, and stabilized the alternator output. I compared the old brushes to new, and they were worn about 50%. So far, so good, but I'm sure a new alternator would be more peace of mind. Thanks for all your informative posts.
Senior Member
Joined: Jul 2015
Posts: 355
Likes: 41
From: amarillo texas
2003 sl 500
Hey Cyglee how hard was it to do that replacement? I assume you put in a new regulator and brush set. I had heard that can be done. What kind of cost? Mine is an '03 also. Sounds like a good thing to know, I am OK now but there may come that day.
moretech
moretech
Thread Starter
MBworld Guru
Joined: Dec 2009
Posts: 10,782
Likes: 1,011
NO LONGER ACTIVE
The regulator comes with brushes. Unless the alternator mechanically fails (bearings) it's usually just the regulator. In my case, the dealer charges almost as much for a regulator as Advance Auto charges for a lifetime warranted alternator (which includes the regulator). I didn't want to wait for delivery so I went with the $180 rebuilt one from AA. I did look at the old alternator. I see no problems with the brushes or rotor. I think mine was heat related because it would work in the morning, then die after everything was warmed up.
Here's the regulator on the alternator:
And the rotor:
And the brushes:
Here's the regulator on the alternator:
And the rotor:
And the brushes:
Junior Member
Joined: Nov 2014
Posts: 58
Likes: 11
2003 SL500
I had read somewhere that MB alternators were rather robust, but the voltage regulators could be a wear issue. So, $82. from FCP, and about 30 minutes working from underneath. It does take some finesse working in tight quarters, and I disconnected both batteries. The top regulator has the shorter, worn brushes.
Thread Starter
MBworld Guru
Joined: Dec 2009
Posts: 10,782
Likes: 1,011
NO LONGER ACTIVE
The alternator on the C240 went almost 170K miles without missing a beat, and that was even after a broken idler pulley shredded the belt and it was sucked into the alternator where I spend a few hours picking it out piece by piece.
I don't think the issue is the brushes. Even being shorter due to wear, they are plenty long. Look at my first pic - there is very little of the brush between the regulator and rotor. Those brushes could be worn much more and still make contact. I think he failure is in the electronics of the regulator.
I don't think the issue is the brushes. Even being shorter due to wear, they are plenty long. Look at my first pic - there is very little of the brush between the regulator and rotor. Those brushes could be worn much more and still make contact. I think he failure is in the electronics of the regulator.
Member
Joined: Nov 2024
Posts: 124
Likes: 5
From: Charleston, South Carolina USA
2004 SL500 Aegean Blue Metallic
I had read somewhere that MB alternators were rather robust, but the voltage regulators could be a wear issue. So, $82. from FCP, and about 30 minutes working from underneath. It does take some finesse working in tight quarters, and I disconnected both batteries. The top regulator has the shorter, worn brushes.
