Im trying diagnose my 05 SL55 with 27k miles. Both batteries are good and alternator is charging and I changed the voltage regulator. Been driving it like this for 2 months. Good job on video, this is in a PIA location, thanks Mercedes engineer.
you should repl the voltage reg on the alternator if it has more than 100k miles on it. the brushes do wear out. the regulators are cheap. we replaced thousands of them on a recall.
Hi, just wanted to say thanks, I've managed to replace the 100 amp fuse (3-pack was 9.99 on Amazon) based on your video. My issue was the starter battery not charging. Now she's purring like new. :)
MB dual battery sytem owners be aware that the RED battery warning light will NOT self-reset - EVEN AFTER YOU FIX THE F52/1 fuse. YEs, the Yellow colored Battery Light WILL self-reset if you have it for some other reason like a simple dead battery or such...but NOT the RED one. So, if you have an F52/1 fuse burnout for any reason, or any other serious electrical problem, the ECU will cook in the RED warning light into its service memory... period. That is why there are two different colored battery warning symbols...something most people miss. Yellow is for routine dead/low battery stuff. RED is a more serious electrical system failure (including F52/1 fuse blown and a lot of other broken stuff alerts) But with regard to this repair, Don't worry about that red battery light too much. If your F52/1 fuse is replaced, and nothing else is broken, the system will return to normal charging (assuming no other electrical system problems exist) Just remember that the RED battery warning light will not go out, ever - until you hit it with a software code reset. If you doubt me, do this simple test for your peace of mind. Do your F52/1 or whatever repair/fuse replacement. Now, open hood, open trunk. and access the two batteries. Put a DVM on each battery with the engine running and measure DC voltage. You should observe about 14.2 - 14.5VDC or so on the positive terminals of BOTH batteries. If you do, then BOTH batteries are charging. There is no other possible explanation for a battery with 14.5 VDC on the terminals. Still doubt? Shut off engine. Measure VDC again on both batteries. It will drop to about 12.7volt or so. The DIFFERENCE between the running voltage and the static voltage is telling you that the alternators are putting CURRENT into the batteries...i.e. they are charging. You are golden. Red warning means nothing. Now, if you don't see 14.2-14.5 VDC on one or the other or both batteries (with engine running) you still have problems...even if you have replaced the F52/1 fuse. This means your alternator is not charging (especially if both batteries are not showing voltage up when engine running) or your BMECU module (in the trunk on the passenger side wheel well, rear facing) if one battery is charging and the other is not charging. Suspect the BMECU is faulty in that case. (assuming you KNOW your F52/1 fuse is good, of course) But again, just fixing the F52/1 fuse will NOT magically eliminate the RED battery light. That error code gets cooked into the ECU memory when it happens. The car will NOT self-heal that warning. As far as I can discover, it can only be purged by using MB compatible ECM control service software (dealer or aftermarket) on a dual battery equipped vehicle (R230/SL500/550 etc.) That is not a simple OBDII reader either, at least as far as I can find. I am talking about the full-on MB service software, which is available semi-pirated...for about a grand or so including the hardware. Or, visit your dealer and ask them to simply reset the light. $96.00 at my dealer. Enjoy your Mercedes!
Great info, thanks. I have the red light on, the consumer battery is charging at 14v with engine running. Front battery does not appear to charge and remains at the engine off rate of 12.6v. Can I rule out the F52/1 fuse? Is it correct to assume the car would not start if this fuse was blown? If this fuse was blown would it come up on the Merc Star diagnostic report? If so I would prefer my local indi to check before doing what looks like a substantial and awkward fuse replacement task. Or is there another way to test this fuse? If the fuse is OK I assume the issue is the BCM a very very expensive part😢
Have a problem, my fromt battery not charging, the rear one 14.2v charging ok. I changed alternator voltage regulator, change front battery, changed 100amp fuse which was blowed up and still not charging. No any red battery lights on dash. So its only can be controle battery unit blowed up? How to check this? Any advise?
@@RadzaLT No, been busy but sure it is the BCM which is no longer made 😡. Suggest you put your car on a Merc Star diagnostic, this will probably provide highlight the issue.
The 100 amp fuses doesn’t turn out your light it simply turns on your alternator. There’s an exciter wire circuit that’s activated by the ECM/ECU that turns the alternator on and off.
Firstly THANK YOU! I actually opened a Insta account to follow you. I think I found the fusebox behind the glovebox, on top of the footwell cover. 1) how do I unclip the three white clips holding the cover onto the box ? 2) is there a way to send you the photo of what I think is the fusebox ? Its kind of round clipped onto a larger round plastic lid.
Hi I have an 2008 sl55 and the consumer unit battery only last overnight then flat. I checked the fuse for the command unit and this was drawing about 2.5 amps. Would this be a fault in the command unit. I was told it maybe something else not allowing the command unit to go to sleep. any help would be appreichiated. Thanks Paul
I have same issue on a car, at parking, batt Is drawning in 3-4 days, under 10v! loosing the accessories, even the inside lamp when u want it back for a ride! I guess as everybody says, change the 100a fuse and see if charging while driving Is More efficient, cuz it s not actualy...
I've got same red batt/alternator ..my front batt seems is charging reading 12.5.. but rear 10.7 volts when car running..do you think alternator ? or this fuse..
@@aroojsyeda I gave up trying to make the warning light go off. Everything is charging and working as it should except for battery light, so I just reset light every time.
Have a problem, my fromt battery not charging, the rear one 14.2v charging ok. I changed alternator voltage regulator, change front battery, changed 100amp fuse which was blowed up and still not charging. No any red battery lights on dash. Any advise? Please help
read about battaries charging cycle - BCM (battery control module) switch which battery is charging ATM. Good that at least rear battery is charging ! That make me think your BCM is good and you don't need to buy it for $1500 pre-owned. In my case - none of the batteries charge after I've replaced altenator :( Hope it's beacuse of fuse. But someone jumstarted car using rear battery, which might burn BCM.....
Do you know why my auxiliary battery would not be charging? Consumer battery is charging from the alternator but it seems no power is going to the front starter battery :/ I replaced this fuse but the problem still persists. Thanks in advance
@@Mr.Affalterbach Thank you for your reply :) I bought 100A. I will replace tomorrow. Hopefully it is burned out cos I don't know what else the problem would be for my car :/
🤔 Battery Warning , Visit Work Shop ? 2006 M-Benz SL 500 I would like to ask for some advice, please? I have a Red Battery Icon & Visit Work Shop message. The engine compartment battery was tested at advanced auto parts & it was good. I replaced the trunk battery, but still get the same battery warning once in awhile. The engine compartment battery's negative cable was disconnected, voltage reading was 13.04 V The trunk battery voltage reading was 12.99 V , with front/engine battery's disconnected.
Have a problem, my fromt battery not charging, the rear one 14.2v charging ok. I changed alternator voltage regulator, change front battery, changed 100amp fuse which was blowed up and still not charging. No any red battery lights on dash. Any advise? Please help
Who couldn't think of a dozen more convenient locations for that fuse? Nicely done! Thank you.
Exactly, I have a feeling that it was MB's way of having their typical customers actually "visit workshop" and charge to replace the module.
I only go to dealer as last resort. Just finished deleting ABC and adding sway bars on 05 SL55.
Im trying diagnose my 05 SL55 with 27k miles. Both batteries are good and alternator is charging and I changed the voltage regulator. Been driving it like this for 2 months. Good job on video, this is in a PIA location, thanks Mercedes engineer.
Thanks for letting us know what size bolts they are
you should repl the voltage reg on the alternator if it has more than 100k miles on it. the brushes do wear out. the regulators are cheap. we replaced thousands of them on a recall.
What size sockets
Hi, just wanted to say thanks, I've managed to replace the 100 amp fuse (3-pack was 9.99 on Amazon) based on your video. My issue was the starter battery not charging. Now she's purring like new. :)
Did the old fuse look broken?
@@benjaminwingchun9665 it did not but when I tested it it definitely was broken.
It’s a deep nut inside of the Bose speaker what size
I'm literally just doing this job, deep 10mm!
Are all the nuts to get the plate out 10 mm ? Having trouble with the bottom ones.
@@YourFajah94 there are a few plastic ones, try a mirror and a light, you really don't want to strip those - sounds like you might have?
@@adamdezsi all good
Nice work, well done dad 😂👍
MB dual battery sytem owners be aware that the RED battery warning light will NOT self-reset - EVEN AFTER YOU FIX THE F52/1 fuse. YEs, the Yellow colored Battery Light WILL self-reset if you have it for some other reason like a simple dead battery or such...but NOT the RED one. So, if you have an F52/1 fuse burnout for any reason, or any other serious electrical problem, the ECU will cook in the RED warning light into its service memory... period.
That is why there are two different colored battery warning symbols...something most people miss. Yellow is for routine dead/low battery stuff. RED is a more serious electrical system failure (including F52/1 fuse blown and a lot of other broken stuff alerts)
But with regard to this repair, Don't worry about that red battery light too much. If your F52/1 fuse is replaced, and nothing else is broken, the system will return to normal charging (assuming no other electrical system problems exist) Just remember that the RED battery warning light will not go out, ever - until you hit it with a software code reset.
If you doubt me, do this simple test for your peace of mind. Do your F52/1 or whatever repair/fuse replacement. Now, open hood, open trunk. and access the two batteries. Put a DVM on each battery with the engine running and measure DC voltage. You should observe about 14.2 - 14.5VDC or so on the positive terminals of BOTH batteries. If you do, then BOTH batteries are charging. There is no other possible explanation for a battery with 14.5 VDC on the terminals. Still doubt? Shut off engine. Measure VDC again on both batteries. It will drop to about 12.7volt or so. The DIFFERENCE between the running voltage and the static voltage is telling you that the alternators are putting CURRENT into the batteries...i.e. they are charging.
You are golden. Red warning means nothing.
Now, if you don't see 14.2-14.5 VDC on one or the other or both batteries (with engine running) you still have problems...even if you have replaced the F52/1 fuse. This means your alternator is not charging (especially if both batteries are not showing voltage up when engine running) or your BMECU module (in the trunk on the passenger side wheel well, rear facing) if one battery is charging and the other is not charging. Suspect the BMECU is faulty in that case. (assuming you KNOW your F52/1 fuse is good, of course)
But again, just fixing the F52/1 fuse will NOT magically eliminate the RED battery light. That error code gets cooked into the ECU memory when it happens. The car will NOT self-heal that warning. As far as I can discover, it can only be purged by using MB compatible ECM control service software (dealer or aftermarket) on a dual battery equipped vehicle (R230/SL500/550 etc.) That is not a simple OBDII reader either, at least as far as I can find. I am talking about the full-on MB service software, which is available semi-pirated...for about a grand or so including the hardware. Or, visit your dealer and ask them to simply reset the light. $96.00 at my dealer.
Enjoy your Mercedes!
Great info, thanks. I have the red light on, the consumer battery is charging at 14v with engine running. Front battery does not appear to charge and remains at the engine off rate of 12.6v. Can I rule out the F52/1 fuse? Is it correct to assume the car would not start if this fuse was blown? If this fuse was blown would it come up on the Merc Star diagnostic report? If so I would prefer my local indi to check before doing what looks like a substantial and awkward fuse replacement task. Or is there another way to test this fuse? If the fuse is OK I assume the issue is the BCM a very very expensive part😢
Have a problem, my fromt battery not charging, the rear one 14.2v charging ok. I changed alternator voltage regulator, change front battery, changed 100amp fuse which was blowed up and still not charging. No any red battery lights on dash. So its only can be controle battery unit blowed up? How to check this? Any advise?
@@dboynette did u manage to fix “front battery not charging” problem?
@@RadzaLT No, been busy but sure it is the BCM which is no longer made 😡. Suggest you put your car on a Merc Star diagnostic, this will probably provide highlight the issue.
My bcm looks good visually but idk both fuses look good . But I can't get car to turn over even with a jump . Red battery light is on also
The 100 amp fuses doesn’t turn out your light it simply turns on your alternator.
There’s an exciter wire circuit that’s activated by the ECM/ECU that turns the alternator on and off.
The 100amp fuse was blown for mine I’ve changed it but the battery warning light still on
If you gonna show how to fix please put nut size everytime you remove the nuts it would help
Firstly THANK YOU!
I actually opened a Insta account to follow you.
I think I found the fusebox behind the glovebox, on top of the footwell cover.
1) how do I unclip the three white clips holding the cover onto the box ?
2) is there a way to send you the photo of what I think is the fusebox ? Its kind of round clipped onto a larger round plastic lid.
Did you replace the starter and AGM batteries with genuine Mercedes bats or aftermarket versions?
Hi I have an 2008 sl55 and the consumer unit battery only last overnight then flat. I checked the fuse for the command unit and this was drawing about 2.5 amps. Would this be a fault in the command unit. I was told it maybe something else not allowing the command unit to go to sleep. any help would be appreichiated. Thanks Paul
was it a bad fuse or "an aging alternator" that caused the battery not charging? I am confused.
Great job 👏🏼
Excellent video 🤘🏻🇬🇧
So whole time it was the fuse?
Hi,
Did your old fuse look broken?
I have same issue on a car, at parking, batt Is drawning in 3-4 days, under 10v! loosing the accessories, even the inside lamp when u want it back for a ride!
I guess as everybody says, change the 100a fuse and see if charging while driving Is More efficient, cuz it s not actualy...
Did you still have to change alternator?? Having same issue with rear batt not charging and front is..?
Hi, do you know a Company the will Refurbish the Battery Control Unit 230-540-10-45-80
I've got same red batt/alternator ..my front batt seems is charging reading 12.5.. but rear 10.7 volts when car running..do you think alternator ? or this fuse..
Sounds more like alternator if you're not getting at least 13V with then engine running
Try the voltage regulator on back of alternator.
@@jmluke1876 do you have a part number for this regulator buddy?
@@aroojsyeda I gave up trying to make the warning light go off. Everything is charging and working as it should except for battery light, so I just reset light every time.
Have a problem, my fromt battery not charging, the rear one 14.2v charging ok. I changed alternator voltage regulator, change front battery, changed 100amp fuse which was blowed up and still not charging. No any red battery lights on dash. Any advise? Please help
read about battaries charging cycle - BCM (battery control module) switch which battery is charging ATM. Good that at least rear battery is charging ! That make me think your BCM is good and you don't need to buy it for $1500 pre-owned. In my case - none of the batteries charge after I've replaced altenator :( Hope it's beacuse of fuse. But someone jumstarted car using rear battery, which might burn BCM.....
My car won't start after changing this fuse it only clicks no crank 😏
Sl500 no heat blowing. Just cold. Only to face. No legs even if selected. After 10 day driving alerneyor not charging now… help?
Good information thank you 👍
Do you know why my auxiliary battery would not be charging? Consumer battery is charging from the alternator but it seems no power is going to the front starter battery :/ I replaced this fuse but the problem still persists. Thanks in advance
Did u manage to fix this problem? Have same one🙈
can you replace this with a 125A fuse?
Id recommend using the same fuse just to be safe. There has to be a reason why its 100a
@@Mr.Affalterbach Thank you for your reply :) I bought 100A. I will replace tomorrow. Hopefully it is burned out cos I don't know what else the problem would be for my car :/
🤔 Battery Warning , Visit Work Shop ?
2006 M-Benz SL 500
I would like to ask for some advice, please?
I have a Red Battery Icon & Visit Work Shop message.
The engine compartment battery was tested at advanced auto parts & it was good.
I replaced the trunk battery, but still get the same battery warning once in awhile.
The engine compartment battery's negative cable was disconnected, voltage reading was 13.04 V
The trunk battery voltage reading was 12.99 V ,
with front/engine battery's disconnected.
My own Mercedes Benz SL500 light is not coming on
Difficult to see with the noicey background music. Beside that, thanks for good movie
It also covers the little cracks AND knocks that can bé worth, but yeah he could set His voice chanel louder 🙂
Thank u so much
Is only 4 nuts not 5 I think
Type car??????
SL 55 AMG...from Mercedes
the audio is not any good
LSD!
Soon!
Quaife style?
I did rebuild of front and rear valve blocks. Does your car pass rodeo without interruptions?
@@pfoxhound hope you are making over $200k/year if you plan on keeping the ABC system.
@@jmluke1876 it is not that bad if you rebuild the abc yourself. I just did my entire abc on my sl500. it is good for 10 years
Have a problem, my fromt battery not charging, the rear one 14.2v charging ok. I changed alternator voltage regulator, change front battery, changed 100amp fuse which was blowed up and still not charging. No any red battery lights on dash. Any advise? Please help