SL/R230: Replacing Voltage Regulator (R230 SL)
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SL500
Replacing Voltage Regulator (R230 SL)
I have a 2006 SL500 so this question applies to 2003 and newer SL's.
I have spent about 40 minutes trying to find instructions on replacing a voltage regulator on a R230 SL500 with no luck.
Does anyone know what's involved in replacing the voltage regulator on a R230 SL? Does the alternator need to be pulled to replace the regulator? Can it be done from above or below?
Also, when I talked to a Mercedes' Tech he said my problem could be caused by a faulty "charge control unit" which applies power to the battery that is weakest."Does anyone have a clue about this charge control unit?
Thanks in advance.
I have spent about 40 minutes trying to find instructions on replacing a voltage regulator on a R230 SL500 with no luck.
Does anyone know what's involved in replacing the voltage regulator on a R230 SL? Does the alternator need to be pulled to replace the regulator? Can it be done from above or below?
Also, when I talked to a Mercedes' Tech he said my problem could be caused by a faulty "charge control unit" which applies power to the battery that is weakest."Does anyone have a clue about this charge control unit?
Thanks in advance.
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From: Charleston, South Carolina USA
2004 SL500 Aegean Blue Metallic
I looks like this question never got answered. So does the alternator need to be removed to replace the voltage regulator? Mine is a 2004 SL500 if that makes any difference.
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From: Charleston, South Carolina USA
2004 SL500 Aegean Blue Metallic
Thanks for the response. Is that from the top or the bottom or both?
I see some replacement parts listed as just a voltage regulator and I see other ones listed as a 14 V voltage regulator. Is there a difference? Is it strongly recommended to go back to an original Bosch supplied regulator?
I see some replacement parts listed as just a voltage regulator and I see other ones listed as a 14 V voltage regulator. Is there a difference? Is it strongly recommended to go back to an original Bosch supplied regulator?
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95 SL600
On other cars like gm and such, the aftermarket would be fine, with this car, I would definitely go with the Bosch. These cars are nonsense with electronics. Make sure you disconnect the back battery first, and then the front one, and reconnect front then the rear
It is all accessed from the bottom.
It is all accessed from the bottom.
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From: Ann Arbor, MI
2004 SL600
Originally Posted by hooperdoski;5402016...
Also, when I talked to a Mercedes' Tech he said my problem could be caused by a faulty "charge control unit" which applies power to the battery that is weakest."[color=#1f497d
Also, when I talked to a Mercedes' Tech he said my problem could be caused by a faulty "charge control unit" which applies power to the battery that is weakest."[color=#1f497d
Does anyone have a clue about this charge control unit?
Thanks in advance.
Thanks in advance.
The alternator connects directly to the rear battery. (Through a 200 Amp fuse.) When the Battery Control Module (BCM) detects that the front battery isn't fully charged, it uses its internal DC-to-DC converter to charge the front battery; I think the max front charging current is about 20 Amps or so.
The simple Alternator test is to start the engine and test the voltage on the rear battery. It should be around 14.2. Anything below 13.5 would be troublesome and indicate an alternator problem.
If you were to detect no increase in voltage with the engine running, then its either the alternator or that 200 Amp fuse. In that case I would next check the voltage on the alternator itself at its big terminal. The 200 Amp fuse is in the 4" black box just in front of the rear battery.
Last edited by mrvedit; Feb 21, 2025 at 04:18 PM.
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2003 SL55 AMG
I did mine a few years ago. It was the first thing I did on my car. The interior lights would slightly pulsate with the engine rpm. The new reg fixed it.
It’s a relative easy procedure. I did it all from the bottom with a real Bosch regulator.
here is a how to:
https://mbworld.org/forums/attachmen...663d1438025955
It’s a relative easy procedure. I did it all from the bottom with a real Bosch regulator.
here is a how to:
https://mbworld.org/forums/attachmen...663d1438025955
Last edited by SL101; Mar 22, 2025 at 02:32 AM.
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From: Orange County, California, USA
2005 FJR 1300, 2007 S550, 2009 SL550, 2010 GL450, 2016 GLE350
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From: Glasgow, Scotland, UK
SL 350 R230 (3.7L with AMG Speedshift autobox)
I did mine a few months back, pretty easy just worked on topside, but its dependant on engine size space, I changed the whole alternator as it was old and not just the voltage regulator.
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From: Charleston, South Carolina USA
2004 SL500 Aegean Blue Metallic
I did mine a few months back, pretty easy just worked on topside, but its dependant on engine size space, I changed the whole alternator as it was old and not just the voltage regulator.
https://youtu.be/9KcKWMhW9ss
https://youtu.be/9KcKWMhW9ss
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From: Glasgow, Scotland, UK
SL 350 R230 (3.7L with AMG Speedshift autobox)
Thank you for your comment. I noticed that you said you took the whole alternator out. So did you only replace the regulator once you got the alternator out from the top? Do you think you could’ve just replaced the voltage regulator from the top? I ask because SL101 says he replaced just the voltage regulator from an underneath the car approach.
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From: Charleston, South Carolina USA
2004 SL500 Aegean Blue Metallic
Thanks. I have read in a few different posts that the regulator can be replaced while on the car. Those posters did not indicate whether it was an approach from the top or the bottom. That’s what I was wanting to clarify. And I don’t know if this is correct but this is what some posters have said: replacing the regulator might be considered good routine maintenance where as you replace the alternator when it fails. I have a lift so the approach from the bottom would be very easy. It looks to me the approach from the top would be difficult, maybe impossible.
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From: Ann Arbor, MI
2004 SL600
Position and best access likely depend upon which engine it is. The SL350 mentioned by @A1EK is a V6 with likelymuch more working space than any V8. ("Working space" and V12 should never be mentioned in the same sentence, unless there is a Negative word.)
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2003 SL55 AMG
Thank you for your comment. I noticed that you said you took the whole alternator out. So did you only replace the regulator once you got the alternator out from the top? Do you think you could’ve just replaced the voltage regulator from the top? I ask because SL101 says he replaced just the voltage regulator from an underneath the car approach.
I also have Kleemann headers on my car, I don't know if that would help or hurt access.
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2009 SL 550; 2022 GLE 450
I changed my regulator 0n my 2003 SL500 from the underneath - look for a video that shows where all the screws are - there is one that is somewhat blind but still accessible from underneath the car. Cheers Socks
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From: Norfolk Va
2003 SL500 1991 190E 2.3 2011 ML350 1998 SL500
I replaced voltage regulator
took alternator out of car from the bottom the alternator is bullet proof
replaced mine as preventive maintenance 145k miles
pretty straightforward job
took alternator out of car from the bottom the alternator is bullet proof
replaced mine as preventive maintenance 145k miles
pretty straightforward job
Member
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Posts: 124
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From: Charleston, South Carolina USA
2004 SL500 Aegean Blue Metallic
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2009 SL 550; 2022 GLE 450
Bob - I searched my links and could not find the video (it was 5 years ago when I replaced my regulator); however, I recall the biggest help was seeing the locations of the regulator screws - the upper screw is the challenge. I used a Phillips head socket on a 1/4 inch rachet but a small 90 degree screwdriver will also. By sensing where the hidden screw is located, it was not that hard to remove the screw even though I could not see it and since both batteries were disconnected I wasn't worried about arching. Also, getting the regulator brushes to clear the armature was not that hard - everything was doable from underneath the car. Sorry I couln't be more helpful. Cheers Socks
