Issue started maybe 2 weeks ago, started the car and was pulling out the driveway when a red battery light came on the dash. Pulled back in, stopped and restarted the car and no more light, no messages in the "service menu". Following week it happened again, before stopping the car i checked the messages in the Service setting on the dash and it said "1" message, when I click to read the battery light showed back on the dash. I stopped and restarted, no more light. It seems to only happen when starting the car at the 1st start of the day, then doesnt come back on.


Photo not from my car, but it is the same exact way it looks on my dash. Nothing about "visit workshop" I noticed.


Went out with my scanner and had it hooked up while I started the car for the 1st time today, the red battery light came on. I went into the alternator setting on the scanner and it had a code "The output for the actuation of the alternator has a malfunction.". Under Status it said both Stored and Current, im assuming the scanner is telling me it has happened before and is happening now.


Old photo, does not have the "current" under status like it now has today.


When I switched to see the current alternator readings I noticed under Battery Voltage it was showing around 11.4v. Also I noticed under "Calculated alternator torque" it was showing around 8nm. Under Mechanical or Electrical fault in alternator both showed "NO".

I did something with the scanner, totally forget what I did, but I switched screens then went back to this screen and the battery voltage was now showing 14.70v and the Calculated alternator torque was showing 19nm. Still showed NO for mechanical and electrical alternator faults.



At first i was thinking of replacing the voltage regulator, but after it saying no faults and then seeing the figures for calculated alternator torque im wondering if it may be the alternator pulley? Could it even be the pulley, i have no idea. its not making any out of the ordinary noises from what i can tell.

I replaced the battery with a mercedes brand battery last year, i also replaced the drive belt last year and just looked at the tensioner and its showing right where it should be.

I have not done any work near the alternator or battery lately. I took off the battery cover the other day to specifically inspect the battery and everything looks fine, no corrosion at the cables, no swelling of the battery or visible leaks.


I recorded that screen on the scanner and looked at it on my computer. Took a screenshot.


Edit: I will add that because I dont really drive the car that many miles I have a Noco Genius 5 charger that I hook up to the battery maybe once a month, let it do its thing until it shows all charged up. I have the cables hard wired, positive to the positive battery post and the negative to the cars ground in the engine bay near the battery. Been using this for many many months.

 

Maybe get a battery alternator tester ($8 on Amazon) to make sure the alternator is working correctly.

https://a.co/d/a8GDopF

 

Im wondering if the 14.7v reading is too high. Or maybe because of my short trips everywhere and i was fiddling with the car to ON while using the scanner the battery voltage was low at 11.8 (im guessing it was around there cant remember exactly) that the battery management system kicked the alternator to charge that high.

Curious what everyones voltage is reading at idle sitting in the driveway?

Ill go for a long drive tomorrow to give the battery time to fully charge, then do more testing.

if it is the battery, which im not really thinking it is, I still have another year on the warranty.

I wonder if my alternator is a remanufactured. Tried taking photos but couldnt really get my phone down in there all to clear, but from what I can see it seems to match with the photo of the Bosch remanufactured alternator on FCP Euro. Theres a little sticker EA something, and the number 48 on it, and the plug is facing out not sideways.

 

[QUOTE=TimC300;8839717]Issue started maybe 2 weeks ago, started the car and was pulling out the driveway when a red battery light came on the dash. Pulled back in, stopped and restarted the car and no more light, no messages in the "service menu". Following week it happened again, before stopping the car i checked the messages in the Service setting on the dash and it said "1" message, when I click to read the battery light showed back on the dash. I stopped and restarted, no more light. It seems to only happen when starting the car at the 1st start of the day, then doesnt come back on[Quote]

That sounds like the battery. If the battery voltage drops below about 10.8 V during cranking, or if it doesn’t recover quickly to about 12.6 V you’ll get the warning. I read the rest of the post and it still could be that the alternator is not getting the battery back up fast enough, or the voltage regulator is developing a leak and the battery is low at first start. At 14.7 V it’s probably charging okay, but the regulator could still be failing. Do you get that warning after your battery maintainer has been on over night?

Most hand held battery testers use about a 50 ampere load which is usually enough. Starters draw more, so a shop will have a multi load tester. Shop testers will also be able to give details about alternator capacity, diodes, and regulator.

 

[QUOTE=Odd Piggy;8839894][QUOTE=TimC300;8839717]Issue started maybe 2 weeks ago, started the car and was pulling out the driveway when a red battery light came on the dash. Pulled back in, stopped and restarted the car and no more light, no messages in the "service menu". Following week it happened again, before stopping the car i checked the messages in the Service setting on the dash and it said "1" message, when I click to read the battery light showed back on the dash. I stopped and restarted, no more light. It seems to only happen when starting the car at the 1st start of the day, then doesnt come back on
Im brain dead so had to go back and look at when I bought the Noco battery charger and it was back on Dec 2 2022, been using it at least once a month since then no issues. Red battery light 1st showed up 2 weeks ago i want to say, so about 9 months using the charger no issues. I dont drive the car all that much, can go 2 or 3 days without using it. I have had the same driving habits with this car since I got it back on 2019, and that battery that came in the car lasted about 2.5yrs before it went dead and wouldnt hold a charge.

I try to think methodically on what the issue could be. Try to think about EVERYTHING I have done that could lead to the issue.

It seems the light comes on the 1st time starting the car if I havent used it in a day or 2. After that I can drive around all day, stopping places and it starts fine no more light. No codes, no rough running, no lights dimming from i can tell etc. I was thinking maybe the brushes in the alternator were sticking at first, or something along those lines, moisture?

The Noco Genius 5 seems to be a good charger/maintainer. It technically should inform me if there is an issue with the battery. I got it specifically so it would hopefully maintain the battery.

Im leaning towards the voltage regulator from FCP $43 (on sale at eEuro for only $26 but out of stock), but then again the alternator does look beat so wondering if its best to just get a new remanufactured Bosch for $254(with FCP lifetime warranty is a plus).

I just came across a very interesting read on the electrical management system. Was in a GLK forum but think it may apply to my car. From my understanding when you start the car the alternator will do a fast charge on the battery from anywhere to 20 seconds to 1hr, then switches to temp-based charging and so on. Ive read it twice now and still have to go back and reread to comprehend what its saying.











Whenever i come across things like this i like to print them out and add them to my binder.

This kind of answers my question about if the 14.7v I was seeing is too high. According to this it can go up to 15v, so i should be ok. Also someone on the GLK forum confirmed theres was at 14.7v.

What does all this mean, I have no idea. It may not even be an issue in my case since the light turns on but doesnt stay on, no visit workshop message either. Under the codes it goes back to stored, and not current.

Lastly GLK forum person with issue ended up replacing the alternator with a used one, said no more issues and they never updated again so guessing that was the fix.

 

I want the battery fully charged so i can play around with the obd scanner so decided to hook up the Noco and I noticed within 5 minutes it was showing green, which is supposed to mean "Bulk charge complete, optimizing battery for extended life". When I hooked it up it did its typical thing, red light blinks, then another red light starts to blink also, then an orange light will blink also then finally green. I think the last time I used the charger was maybe 3 weeks ago, last long trip on the highway was 2 weeks ago. Just short trips the past 2 weeks. Leads me to think the battery is holding a charge good, and alternator is working. I could be wrong, just thinking out loud.


It was blinking green within 5-10 minutes. I usually just hook it up and close the hood and let it do its thing. I was fiddling around looking at the belt, for leaks, at the pulleys etc and looked over and sure enough it was green already.


Heres how i have it hooked up. I have the harness hardwired, positive to the positive battery post and the negative to the negative ground on the strut tower where the negative battery cable is also grounded. I read it is best to do it this way so the ground is connected after the battery sensor on the ground wire.


I fish my extension cord through the front grill so i can close the hood. I dont keep the charger in there, just when im charging the battery. No need to keep it in there to just get trashed.

Inspected the battery and connections again, all looks great.

Thinking of keeping my eyes open for a good used alternator. Wondering how much it costs to have an alternator rebuilt, like remove mine and bring it somewhere locally, or buy a used one and ship it off somewhere? Is that more cost effective than buying a new remanufactured alternator? I noticed the remans require a core charge, so they are rebuilding those, im assuming.

 

Here are some options from RockAuto.com, which is a reliable on-line vendor. You will pay shipping extra, and pay shipping on core returns, but there are a couple alternators that do not require you to return the core.

https://www.rockauto.com/en/catalog/...generator,2412

First, I would spend $8 and get a battery alternator tester before throwing parts at the car.

 

If we can’t solve this among ourselves, we shouldn’t have older Benzes (he, he, he!). I’m interested in what you have found. It looks like it is out of the WIS.

The electrical systems on all the 204s (W, S, X) are basically identical except during the model run MB made, I think, 2 changes under that “MB reserves the right to …” clause. So to get really technical, you have to be able to determine your variant. But I don’t think we need to go that deep.

But right now I’m foreman on a construction project we’re doing, so I’ll try to read it and reply when I get home.

 

Heres the PDF of that GF54.10-P-1060CE if its easier to download and view/print.

 

I did look at that tester and not sure it will really help. Description says Max current and voltage 13.9v- 15a, and since it appears the Mercedes alternator charges above that 13.9v is it going to be showing a fault. I have a decent digital multimeter that can probably give me the same if not more info, multimeter will give me the actual readings. That alternator tester reminds me of the little electrical socket tester i have, just two wires hooked up to a light bulb, stick the leads in the socket and if it lights up you know the socket is still live. I can use a multimeter instead which will show me if the socket is still powered and what voltage is there. It also seems like the "issue" is occuring right after I start the car then fixing itself. I think i need to figure out what is happening at this point. Could just be worn brushes.

Heres what that testers instructions say:

Note:

1.Don’t connect the battery for a long time.

2.When car is energized and not started,it detects the voltage of the battery. If the voltage value is lower than 10V (OK led flashing), it is hard to start; if it is lower than 11.6v (low led flashing), please turn off the electrical appliances on the car and start alternator to charge immediately

3.When the car starts, it detects the voltage of alternator.Lower than 13.5v (good led flashing), it can’t charge the battery. You need to check the alternator or turn off some car electrical appliances. Above 14v (fault light flashing or on), check the engine.

Like I said we already know im over 14v with the car running. The tester seems to just measure voltage and flash an led light accordingly.

I havent looked at any other alternators except mercedes and Bosch. I wasnt sure if an aftermarket or off-brand one would be worth trying.

 

I just read there is a menu you can access that shows the cars voltage, before starting and then when the engines running. Says to do:

1. Enter the vehicle and close all doors.
2. Insert the key and turn it to position 1 (the first click, i.e. accessory).
3. If it isn't already there, scroll the MFD to the "default" display for the vehicle speed.
4. Press the reset stalk three times quickly

Ill have to give this a try. Interesting.

 

I don’t think that battery management system is applicable to your vehicle. First, it’s far more complicated than I remember the 204 battery/alternator system being. Second, it refers to “regenerative braking.” There was a GLK hybrid concept car shown at the 2008 Geneva Auto Show. I think that’s what this refers to and the battery they’re managing is the lithium hybrid battery. From what I can find, no GLK with regenerative braking every made it to the showroom.

So back to basics. 14.7 V is the standard output of the voltage regulator on an alternator charging a lead acid battery. A lead acid battery needs more than 0.2 V per cell over-voltage to overcome internal resistance. That is 1.2 V for a 12 volt battery whose nominal voltage is 12.6 V, so there’s 13.8 V minimum for reasonable charging success. At 0.35 V over-voltage per cell, the chemistry of the battery begins to change, the electrolyte begins to boil off, and the plates begin to get damaged. That’s 2.1 V for a 12 volt battery or 14.7 V and why the regulator on the alternator limits the output to that.

Of course, none of that theory solves your problem.

I agree with JettaRed in that testing before buying parts is better than spending $200 for a battery or $250 for an alternator when it’s undetermined which one is at fault. You could spend twice what you need to if the first guess is wrong. Here’s a suggestion. If you have a national chain auto parts store like AutoZone or O’Reilly near by, they have pretty decent hand held battery/alternator testers. The problem is finding the person there who actually knows how to use it properly. They usually have a bona fide auto tech on staff who does. Those testers can show battery state of charge and capacity, alternator output and regulator function and diode integrity. It usually takes at 3-5 minutes to do those tests, not 30 seconds, and if the battery shows under charged at the start, most of them can’t be done at all.

 

On my 2015 SL400, the speedo (multifunction) display showing 5 or 6 different informational displays (mileage, speed, fuel efficiency, driving range, etc.) shows both current fuel consumption and a charging status when slowing down using the brakes on the RANGE display. That's probably what is referred to as "regenerative braking". That feature is NOT present in my 2014 C350, so I doubt it would be present in a 2010 model.

 

Hmmm, maybe not "regenerative braking". That seems to be a term reserved for electric vehicles.

 

The Charge also occurs when coasting downhill.

 

I could be totally wrong but reading it it says "charging in deceleration mode" where the description says charging voltage increased to up to 15v. I couldnt find anything specific to Mercedes just yet but from searching around I came across articles saying this:

"Regenerative braking is an energy recovery technology that takes the kinetic energy of the vehicle that is normally converted into wasted heat in the brake pads and discs during braking and instead converts it into electrical energy to re-charge the starter battery. This is made possible because of the use of smart alternators that can be controlled by the ECU when deceleration is detected. During deceleration (for example when taking your foot off the accelerator) the ECU boosts the alternator voltage output as high as 15V+ to create a burst of charge into the battery. This high voltage puts an increased mechanical load on the engine, resulting in increased engine braking, meaning less of the kinetic energy is converted to wasted heat in the pads and discs. So the deceleration of the vehicle is putting charge back into the battery, saving fuel that would otherwise be required to re-charge it. This charge is then used to power the vehicle's electrical systems when the vehicle is accelerating or travelling at constant speed. During this time the alternator output voltage is reduced (to as low as around 12.5V), which reduces the load on the engine with a consequent reduction in emissions.

Regenerative braking is only effective if the starter battery has some spare storage capacity to absorb the charge created by the alternator during deceleration. If the starter battery was fully charged the electrical energy created would be wasted and so the ECU aims to maintain the battery at around 80% state of charge (low enough to have spare storage capacity but high enough to guarantee engine starting if required).".

Seems pretty straight forward, take your foot off the gas, cars computer detects this, ups the alternator voltage to use the cars coasting energy to fast charge the battery. I do notice on my car it will slow down if i take my foot off the gas, noticable. I dont mean it stops but it certainly does not feel like its coasting,

I also searched around for what the "ME-SFI control unit" even is. This is mentioned in the 1st paragraph of that document I previously posted.







Appears the W204 has that ME-SFI control unit (N3/10)".

Im just having fun looking at all this info. I dont plan on buying anything until i figure out exactly what I think the issue could be. Though looking at my alternator i dont think it would be a bad purchase and not having to worry about it down the road failing, like this winter during a blizzard.

While the weather is nice id like to get everything done, thats how im looking at it.

Also in the 2nd page of that article above it mentions a pyro fuse, is there really one installed in the car?

 

I’ve had a lot of 204s apart and never encountered this. Or didn’t recognize it if I did. So I went to my 2 factory trained tech references. One said no Mercedes until 2019 had anything like that, but all nonAMG cars 2022 and later do. Interesting. But the other said that some 2015 X204s had that system. It was random, not an option, and was the test bed for development so data could be collected. But all the cars that had it had a “lifetime” lithium high capacity starting battery, not a lead acid one. My 2015 GLK owners manual had an insert that made reference to a lithium-carbon battery that would not need replacement. But my SUV had a regular lead acid battery.

Learn all you can. It’s a good thing. Just be aware that Mercedes (and probably every other manufacturer) is not totally transparent on the developing changes in their cars.

 

I forgot to add this little bit of info i remembered. This issue with the red battery light coming on did seem to start around the time I started leaving my headlights to "Auto". I did just recently start doing that. Once in awhile i would look outside at night and see the front passenger parking lights flashing on and off, sometimes would just stay on. I would go outside and rotate the switch, turning it all the way counter clockwise then back to off which seemed to work most of the time, if not i would go back outside and flip it to auto for the night. That issue was so intermittent. Not sure if its related though since everytime the red battery light has come on it was daytime and headlights never were on.

I charged the battery last night, today the car started fine no battery light.

 

Still havent figured out what the issue is. Odd but the red battery light does seem to only come on if I havent started the car for over 1 day. When it does come on the car will just be idling, I will start the car then wait a minute or two and it will come on, car doesnt have to be put in drive or anything.

I went ahead and ordered the Ancel BM200 battery tester. I chose this tester because it has bluetooth and the features seem usefull, looks like it records everything in graph form. So hopefully I can hook it up, start the car and see exactly what the battery voltage is doing. I like the spade type connectors because the clamp type dont seem to fit with the big plastic vent box thing that goes above the battery and I want to drive around with it connected. Im cheap so I searched for the lowest price and ordered it off Aliexpress for only $11.42 shipped.

 

Maybe in time for Christmas?

 

Ha, I know right. Actually ive received most of my orders fairly quick. This one says 12 day shipping so hopefully get it quick. I ordered a 1/4 torque wrench off Harbor Freight 8/26 and they shipped it 8/29 and its now 9/9 and fed ex still hasnt delivered it. Thats the only thing holding me up doing my transmission fluid. I have to force myself to log off AliExpress because I find so much junk I want to get.

 

Received the battery monitor today. Strangely enough the battery light has not come on since. May be just a freak issue that cleared itself up. Going to install this thing and see what it can tell me.

 

Not a chance. Those things wait until the absolute worst time to return. As in: Jump in car to flee wildfire > Turn key > Nothing. 😳

 

Probably. At least it hasnt effected the car, yet. Its making me look for the problem. I thought it had something to do with being parked over 1 day but thats not the case, had a big storm the past weekend and it was parked well over 2 days in the cold, rain, and started fine no light.

I downloaded the app for the battery monitor to my phone and dont like how it wants so many permissions, wants your location, camera, photos, email, cant open the app without accepting and the app stays on. I did a little research and seems it tracks and collects location data, sends it overseas to Hong Kong. The terms of service mentions giving data to 3rd parties. But I realized its only with Android 6 or later so I deleted it from my phone and got out an old phone and was able to use the app without all the permissions even signing on as a guest. My old phone works its just not activated, got a new phone because it wouldnt hold a charge long anymore. If I had known this I wouldnt have bought it, would of went with a regular monitor that doesnt make you sign up to anything, theres no reason for it in my opinion.

 

“… seems it tracks and collects location data, sends it overseas…”
Side issue: Brace yourself. When you buy a new car (we have 2 ‘cell phones on wheels’), they make you sign authorization to send everything the new ones collect (it’s a lot) to MB and their partners.