Battery/Alternator Fuse?
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09 S63
Battery/Alternator Fuse?
I have an 03 with a bad alternator, replaced it with a reman one from AutoZone, car started fine, it was charging fine and all of a sudden it stopped. I don't want to pull the alternator out to get it tested so want to cover all my bases first, is there a FUSE for the alternator? I always thought they ran all the time but I was told no that they are turned on and off depending on the load required. Can anyone tell me where the fuse for alternator is located on an 03 E55? Thanks ahead of time...
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From: Canada
07 E63 + 07 CLK63CAB
Stopped charging? If your battery was low then probably the reman could not handle the heat or load in this case. Were both batteries in the car tight on the connections and good condition.
What is it showing for voltage now engine off and then started?
What is it showing for voltage now engine off and then started?
Thread Starter
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09 S63
Everything was secured tight. Both AUX & Main battery are pretty new. When I fired the car up after the install, it displayed the battery conv display and then it went off. Drove to the parts store to get some 3M tape to install my lip, and the dash went crazy throwing all kind of lights. got the car home safe and started diagnosing. I have the STAR tool so I will clear all codes, re scan and then do the BCM reset and see what happens. The alternator seemed to work fine but it may have stopped charging after a split second of being on, cant confirm when it "stopped charging"
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From: Canada
07 E63 + 07 CLK63CAB
No that is the good thing, reman is not always the best place to go unless you know the builder.
You will be back on the road soon.
Just call it getting familiar with your car.
You will be back on the road soon.
Just call it getting familiar with your car.
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From: Canada
07 E63 + 07 CLK63CAB
Denis E55, you probably know this already but just in case or for others, always disconnect the negative terminal at all battery sources as (2) in the 55 series when working on electrical equipment, especially alternators, a miss guided wrench or ratchet could be instantly turn into a red hot chunk of metal if shorted out. This also makes failure of your new alternator a for sure thing and possibly some wiring can be destroyed.
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2003 mercedes e500
Battery warning lights visit workshop
hi, I have a 2003 mercedes e500 with battery warning lights visit workshop, batteries checked good, voltage regulator checked good, the ×4/10 fuse checked good, alternator is not charging the battery, when I start the car the voltage on the alternator doesn't increase, so I'm suspecting on the alternator. but there is one thing I haven't checked which is the auxiliary battery relay and the question here is Can a faulty auxiliary battery relay prevent the alternator from charging? Or is it only its properties to control sending and stopping current to the battery?? any opinions or suggestions will be appreciated.
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2006 CLS55 AMG, 2005 SLK 350 AMG
hi, I have a 2003 mercedes e500 with battery warning lights visit workshop, batteries checked good, voltage regulator checked good, the ×4/10 fuse checked good, alternator is not charging the battery, when I start the car the voltage on the alternator doesn't increase, so I'm suspecting on the alternator. but there is one thing I haven't checked which is the auxiliary battery relay and the question here is Can a faulty auxiliary battery relay prevent the alternator from charging? Or is it only its properties to control sending and stopping current to the battery?? any opinions or suggestions will be appreciated.
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2003 mercedes e500
I'd be looking at the Battery Control Module. You can check current to the relay and whether it is switching when commanded to so so as a confirmation. Where did you check the alt voltage output - at the alt or at the battery? To answer your specific question about the relay - no the relay will not impact the alt voltage output. The relay is only a switch which is controlled by the BCM to switch on and off as the aux battery needs charging.
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2006 CLS55 AMG, 2005 SLK 350 AMG
thanks very much for the reply, I really appreciate it. I have checked both, at the alternator, I have confirmed all voltage Measurements and tests and I don't see no problem, also the alternator battery terminal B+ is good, the two wire connector that go to it is good, ground is good. so did you mean that a faulty BCM can prevent a good alternator from charging? If so, can you tell me how to check it.
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2003 mercedes e500
both of my batteries are one year old, from the dealer and I have only 300 miles on them, Since I haven't driven it in about 10 months
Last edited by Obaid1999; Sep 23, 2022 at 03:58 PM.
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2006 CLS55 AMG, 2005 SLK 350 AMG
ok it looks like my battery it won't reach the fully charged any more since it's been a while trying to figure out this issue, and I keep charging it with the trickle charger, the charger was connected to the battery since yesterday and it was showing that the battery is full, but when I checked the voltage on the battery it was 12.37 and when I started the car it was actually 12.00v and 11.70 at the alternator.
both of my batteries are one year old, from the dealer and I have only 300 miles on them, Since I haven't driven it in about 10 months
both of my batteries are one year old, from the dealer and I have only 300 miles on them, Since I haven't driven it in about 10 months
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2003 mercedes e500
Several issues - first, if your alternator is reading 11.7 volts then it is not charging. When it is working properly in should be over 13 volts. You need at a minimum a new voltage regulator on the alt or an all new alt. Not a reman from AutoZone or such - they are total junk (this assumes you are located in the US). These cars need top quality alts. Next, how have you been maintaining the batteries while the car has been sitting for 10 months?
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2006 CLS55 AMG, 2005 SLK 350 AMG
Deep discharging of the batteries will shorten the life and impact how well you can get a full charge back into it. Some batteris will never recover from a deep and long discharge. When you charge the main battery you are not charging the aux battery. It must be charged separately. When the car is running and charging the BCM controls which batteries need to be charged and send current to it.
Some higher end battery chargers can go through a re-conditioning and may be able to resolve the issues of not getting to a full charge. Some of the Ctek chargers have that feature. One thing to be careful of is when the batteries have discharged and the car is started - by jump start or other means, then the alt is maxed out trying to charge those fully discharged batteries. More that one alt have been burned out going through something like that.
Some higher end battery chargers can go through a re-conditioning and may be able to resolve the issues of not getting to a full charge. Some of the Ctek chargers have that feature. One thing to be careful of is when the batteries have discharged and the car is started - by jump start or other means, then the alt is maxed out trying to charge those fully discharged batteries. More that one alt have been burned out going through something like that.
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2003 mercedes e500
Deep discharging of the batteries will shorten the life and impact how well you can get a full charge back into it. Some batteris will never recover from a deep and long discharge. When you charge the main battery you are not charging the aux battery. It must be charged separately. When the car is running and charging the BCM controls which batteries need to be charged and send current to it.
Some higher end battery chargers can go through a re-conditioning and may be able to resolve the issues of not getting to a full charge. Some of the Ctek chargers have that feature. One thing to be careful of is when the batteries have discharged and the car is started - by jump start or other means, then the alt is maxed out trying to charge those fully discharged batteries. More that one alt have been burned out going through something like that.
Some higher end battery chargers can go through a re-conditioning and may be able to resolve the issues of not getting to a full charge. Some of the Ctek chargers have that feature. One thing to be careful of is when the batteries have discharged and the car is started - by jump start or other means, then the alt is maxed out trying to charge those fully discharged batteries. More that one alt have been burned out going through something like that.
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2006 CLS55 AMG, 2005 SLK 350 AMG
Thank you very much for your interaction with my issue. yes, the first time I've removed them out of the vehicle and fully charged them Individually, But since I found out that there is a problem with the charging system, I kept them connected and I wired a wire from inside the house to the backyard and kept the charger outside and whenever the voltage went down, I recharged them. I'm using this raggedy charger, on this setting, I've always hear that the slower charger is the better, it has 2 amp and 10 amp, but I've never used the 10 amp setting
When you have the alt isue resolved make sure the batteries are fully charged before you start the engine and put a load on the new alt.
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2003 mercedes e500
I'd be looking at the Battery Control Module. You can check current to the relay and whether it is switching when commanded to so so as a confirmation. Where did you check the alt voltage output - at the alt or at the battery? To answer your specific question about the relay - no the relay will not impact the alt voltage output. The relay is only a switch which is controlled by the BCM to switch on and off as the aux battery needs charging.
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2006 CLS55 AMG, 2005 SLK 350 AMG
Yes, I definitely need an alternator, but since I read a lot of posts, from people who had the same problem, some changed the alternator and the problem was not solved. Because the charging system in this vehicle is complex, as it contains many components, I wanted to make sure that there was no possibility that one of them could be the obstacle to the alternator. now that you told me that the faulty auxiliary battery relay will not impact the voltage output. So, in my opinion, a defective BCM will not affect the voltage output either. Are you with me on this?
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2003 mercedes e500
If you get your car connected to MB Star diagnostic tool, that will give you a lot more info to make your decision. Star will likely give you the specific current faults that will give you clarity and testing to confirm. It also can query each component so you can see how each functions. I have captured some Workshop info on the BCM and how the two-battery system operates. As you will see there is no mention of the BCM having any control of the alt but it does control the current flow from the alt and how it is managed. I hope this helpful.
Last edited by Obaid1999; Sep 25, 2022 at 03:42 PM.
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04 E55 AMG (totaled), 07 S550 4Matic, 14 E63S
Charge both batteries. Record the codes just in case, then clear all of them. Start the engine, let it run a few minutes, then shut off and check codes. That MIGHT give you a direction but I doubt there is any code that will tell you voltage regulator vs alternator.
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2006 CLS55 AMG, 2005 SLK 350 AMG
Correct - all that may be reported is low voltage output from the alt.
