SL/R230: Starter Battery Low Voltage and Red Warning Light
09-19-2024, 05:34 PM
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Starter Battery Low Voltage and Red Warning Light
I have looked around through the forum for a similar situation, but have not found (or may have missed) one. Disclaimer - I am obviously (as you will see) not too mechanically inclined, but I do sometimes figure things out.
The car, a 2004 SL500 with 86,000 miles is driven once or twice a week for 20-40 miles each time. It started without problem and was running fine - everything working. Then the Electric Consumers Offline warning began to come on- intermittently at first. I thought maybe I was not driving it enough to charge the consumer battery, so I drove farther. The warning would go off, then come back on. Eventually, it just stayed on. Shortly after that, the red warning light came on. The car continued to start without trouble, but nothing else was working so, of course, I did not drive it for about a month until yesterday.
I replaced the consumer battery yesterday because the old one, although only a few months old and still under warranty, was quite dead and I did not trust it- even if taken to the parts store for recharging. I followed the correct installation procedure. The car started right up and everything was working as it should - but the red light remained on.
I took the car to a local shop to have both batteries tested with the car running and with it off thinking maybe I could learn if the batteries are charging properly and possibly rule out the alternator and fuse, etc. With the car not running, the starter battery read only 5.6 volts (keeping in mind the car has not been driven for a month). Running, it read 14.2 volts. The new consumer battery read around 14 volts both running (a little over) and not (a little under).
I am wondering:
1) Perhaps the starter battery is going- or has gone bad- even though the car starts right up? I am not sure how old that battery is, but I have not replaced it during the 5 years I have had the car.
2) could it be that everything is OK and I just need to drive and let the starter battery charge?
3) As for the red light- do I just need to have the code reset by a mechanic or could a dying starter battery cause it to come right back on?
Possibly unrelated, but odd: The remote trunk release on the driver's door has not worked since I have had the car. Yesterday after I installed the new consumer battery, it began working. The soft close still does not work- but I can at last open the trunk without a key. The fobs have never, and still do not work - although both have new batteries.
The car, a 2004 SL500 with 86,000 miles is driven once or twice a week for 20-40 miles each time. It started without problem and was running fine - everything working. Then the Electric Consumers Offline warning began to come on- intermittently at first. I thought maybe I was not driving it enough to charge the consumer battery, so I drove farther. The warning would go off, then come back on. Eventually, it just stayed on. Shortly after that, the red warning light came on. The car continued to start without trouble, but nothing else was working so, of course, I did not drive it for about a month until yesterday.
I replaced the consumer battery yesterday because the old one, although only a few months old and still under warranty, was quite dead and I did not trust it- even if taken to the parts store for recharging. I followed the correct installation procedure. The car started right up and everything was working as it should - but the red light remained on.
I took the car to a local shop to have both batteries tested with the car running and with it off thinking maybe I could learn if the batteries are charging properly and possibly rule out the alternator and fuse, etc. With the car not running, the starter battery read only 5.6 volts (keeping in mind the car has not been driven for a month). Running, it read 14.2 volts. The new consumer battery read around 14 volts both running (a little over) and not (a little under).
I am wondering:
1) Perhaps the starter battery is going- or has gone bad- even though the car starts right up? I am not sure how old that battery is, but I have not replaced it during the 5 years I have had the car.
2) could it be that everything is OK and I just need to drive and let the starter battery charge?
3) As for the red light- do I just need to have the code reset by a mechanic or could a dying starter battery cause it to come right back on?
Possibly unrelated, but odd: The remote trunk release on the driver's door has not worked since I have had the car. Yesterday after I installed the new consumer battery, it began working. The soft close still does not work- but I can at last open the trunk without a key. The fobs have never, and still do not work - although both have new batteries.
09-19-2024, 07:07 PM
#2
Replace both batteries, and do so every 3 years. This is a very important maintenance item on this car. These cars have lots of parasitic drains and don’t like weak batteries. They also have a common propensity to catch the battery control module and wiring in the trunk on fire. This particular device and wiring is 8 or 9 inches from the gas tank FYI.
Do not jump start these cars, as it seems many of the issues can be related to that, and parasitic drains , which lead to bad batteries. It should be noted that if your Battery control module goes bad, which controls the convenience features and charging of the battery they are at the present time NLA and used ones are $2000 or so, and,used.
The Mercedes batteries aren’t that expensive from Mercedes and may be better. I have lots of cars and will put Walmart batt In many of them, but not the r230. These cars will literally burn you if these issues are taken lightly.
Do not jump start these cars, as it seems many of the issues can be related to that, and parasitic drains , which lead to bad batteries. It should be noted that if your Battery control module goes bad, which controls the convenience features and charging of the battery they are at the present time NLA and used ones are $2000 or so, and,used.
The Mercedes batteries aren’t that expensive from Mercedes and may be better. I have lots of cars and will put Walmart batt In many of them, but not the r230. These cars will literally burn you if these issues are taken lightly.
Last edited by cdk4219; 09-19-2024 at 07:08 PM.
09-19-2024, 09:30 PM
#3
Super Member
The starter battery typically lasts much longer than the rear battery but it does sound like yours is on its way out. It can be low and still crank the car OK. If it's low, or the rear battery went low you can get the red light.
As advised, replace the front battery and check the charge on both. Then disconnect both negatives, rear first, then leave the car overnight and the red warning should disappear. If not it doesn't mean there's a fault, you'll just have to clear the stored code with a scanner.
The battery module in the 230 will throw the red light at any minor provocation.
You can safely jump start the car from the front battery only.
As advised, replace the front battery and check the charge on both. Then disconnect both negatives, rear first, then leave the car overnight and the red warning should disappear. If not it doesn't mean there's a fault, you'll just have to clear the stored code with a scanner.
The battery module in the 230 will throw the red light at any minor provocation.
You can safely jump start the car from the front battery only.
09-19-2024, 10:06 PM
#4
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I have a W204 and only have one battery under the hood. I had the car a few years then one day it wouldnt start so i looked at the battery and noticed a date stamped on one of the battery posts, forget if it is positive or negative. Also there is a small circle like a peep hole that was glowing green. Appeared the battery was 7yrs old based on the date, and the label on the battery although in German I could tell if the green is glowing it means its time to replace. i picked a new battery up at my local MB dealer for around $200, i had to bring the old battery back to get my deposit back of $30 I think it was. Came with a 2yr warranty from date of purchase. Try looking for a manufacture date somewhere on the battery to see how old it is.
I dont drive my car many miles, if I dont drive the car for over 2-3 days a red battery warning will pop up as im pulling out of the driveway, though if I pull over at the end of the street, stop and restart the car its fine and doesn't come back. I have no idea what it means, i tried figuring it out but came up with nothing. I even bought two different inexpensive car battery testers, everything checks out fine.
I even bought a Noco Genius 5 battery charger and will charge the battery once a week, just run an extension cord out to the car and it usually takes around 3hrs to do its thing. If you have a garage its probably even easier. I feel better using the charger every so often since it says it "reconditions" the battery, hopefully its working to keep it in good working condition. i have the harness installed in the car so i just have to run the extension cord and plug in the charger, I can just fit the end of the extension cord through the grill so i can close the hood, I feel better not having the hood open. I've used a battery jump pack a few times on my W204 to start it just fine, hook it to the jump start terminals. For the Noco harness I have it wired directly to the positive battery post then have the ground connected to the same ground in the engine bay that the battery is grounded to, i heard its best to hook up after the battery sensor.
I have a Foxwell NT530 OBD scanner with Mercedes software that comes in handy also. When I scan the car I sometimes get a stored code for the actuation of the alternator, no idea what it means and doesnt seem to be that much of an issue so i ignore it mostly. maybe invest in a scanner so you can check for any faults with yours.
I really dont know much about electrical issues but it seems if a battery is allowed to go down past 12v for extended periods of time its not good. 5.6v seems really low. back to my Noco charger, there is a "repair" function on it that is supposed to revive dead batteries. I dont think it will bring it to new condition, more like let you get another month or two out of the battery while you look for a new one.
I dont drive my car many miles, if I dont drive the car for over 2-3 days a red battery warning will pop up as im pulling out of the driveway, though if I pull over at the end of the street, stop and restart the car its fine and doesn't come back. I have no idea what it means, i tried figuring it out but came up with nothing. I even bought two different inexpensive car battery testers, everything checks out fine.
I even bought a Noco Genius 5 battery charger and will charge the battery once a week, just run an extension cord out to the car and it usually takes around 3hrs to do its thing. If you have a garage its probably even easier. I feel better using the charger every so often since it says it "reconditions" the battery, hopefully its working to keep it in good working condition. i have the harness installed in the car so i just have to run the extension cord and plug in the charger, I can just fit the end of the extension cord through the grill so i can close the hood, I feel better not having the hood open. I've used a battery jump pack a few times on my W204 to start it just fine, hook it to the jump start terminals. For the Noco harness I have it wired directly to the positive battery post then have the ground connected to the same ground in the engine bay that the battery is grounded to, i heard its best to hook up after the battery sensor.
I have a Foxwell NT530 OBD scanner with Mercedes software that comes in handy also. When I scan the car I sometimes get a stored code for the actuation of the alternator, no idea what it means and doesnt seem to be that much of an issue so i ignore it mostly. maybe invest in a scanner so you can check for any faults with yours.
I really dont know much about electrical issues but it seems if a battery is allowed to go down past 12v for extended periods of time its not good. 5.6v seems really low. back to my Noco charger, there is a "repair" function on it that is supposed to revive dead batteries. I dont think it will bring it to new condition, more like let you get another month or two out of the battery while you look for a new one.
09-20-2024, 11:52 AM
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I really appreciate the replies and advice. This weekend I will replace the starter battery (will disconnect consumer battery first per procedure). I will also try disconnecting both negative leads overnight to see if the red light will go away. I will buy the battery at a national chain parts store rather than the dealer because I can get a significant discount.
Off topic stuff I should probably put somewhere else...
This car has started to worry me! I loved it when I bought it- beautiful style, fun to drive, reasonably comfortable for a tall guy. In 44 years of driving, I have owned 6 convertibles of various makes and ages, This is the first of them you can have a normal conversation while driving with the top down. My SL was babied by the first owner and I bought it in like-new condition with only 35k miles. It still looks like new and my friends are surprised it is 20 years old. But then the troubles started...
So far, on a trip last October the ABC suddenly blew a hose. If it wasn't so serious, the boingy ride was kind of funny. Luckily I was a mile from the repair shop I was using - until I learned the guy was a crook. He took me for about $3k before I found out! He skipped town with many peoples' money. The second shop, very near the first one, took 3 months to get the job, promising all the while he would get it done quickly - all the while other cars were coming and going. So he is also off my list. I will say of him that once the repairs reached half the current value of the car, he advised me to let him stop- although there was still a mysterious issue with the rear left strut (no current warnings or codes on that). The nearest dealer's shop is ridiculously expensive - and the second guy (the one who took so long) is associated with that dealer.
On another trip this past May, the transmission went into limp mode 600 miles from home. Luckily, that time we were about a mile from our destination. It was fine the next morning. I suspect the transmission fluid is low and was very surprised I could not check it! The transmission has probably never been serviced- so that needs to be done and is next on the list. Before I could get that done, the current problems started.
Now dealing with the electrical gremlins and warnings of potential for fires (yikes!). I hated to do it, but the car was banished from the garage in favor of my much simpler to repair 1958 Buick. At least the Buick is less likely to burn the house down.
Now I just need to find somewhere to have the SL repaired that is reasonable, works quickly, and is trustworthy. I have heard of two places, both three hours from where I live in west-central Alabama. Both are near Birmingham. One is in Hueytown and another in Trussville. In short, this is not an easy car to own! A convertible is not fun if it can't be driven. I'd sell it but I am too upside down with it financially. I cannot find anything I like better that is any more reliable. I thought about a Corvette, but my wife dislikes them. Plus, to me, a corvette looks too much like mid-life crisis while the SL looks more like successful attorney.
Off topic stuff I should probably put somewhere else...This car has started to worry me! I loved it when I bought it- beautiful style, fun to drive, reasonably comfortable for a tall guy. In 44 years of driving, I have owned 6 convertibles of various makes and ages, This is the first of them you can have a normal conversation while driving with the top down. My SL was babied by the first owner and I bought it in like-new condition with only 35k miles. It still looks like new and my friends are surprised it is 20 years old. But then the troubles started...
So far, on a trip last October the ABC suddenly blew a hose. If it wasn't so serious, the boingy ride was kind of funny. Luckily I was a mile from the repair shop I was using - until I learned the guy was a crook. He took me for about $3k before I found out! He skipped town with many peoples' money. The second shop, very near the first one, took 3 months to get the job, promising all the while he would get it done quickly - all the while other cars were coming and going. So he is also off my list. I will say of him that once the repairs reached half the current value of the car, he advised me to let him stop- although there was still a mysterious issue with the rear left strut (no current warnings or codes on that). The nearest dealer's shop is ridiculously expensive - and the second guy (the one who took so long) is associated with that dealer.
On another trip this past May, the transmission went into limp mode 600 miles from home. Luckily, that time we were about a mile from our destination. It was fine the next morning. I suspect the transmission fluid is low and was very surprised I could not check it! The transmission has probably never been serviced- so that needs to be done and is next on the list. Before I could get that done, the current problems started.
Now dealing with the electrical gremlins and warnings of potential for fires (yikes!). I hated to do it, but the car was banished from the garage in favor of my much simpler to repair 1958 Buick. At least the Buick is less likely to burn the house down.
Now I just need to find somewhere to have the SL repaired that is reasonable, works quickly, and is trustworthy. I have heard of two places, both three hours from where I live in west-central Alabama. Both are near Birmingham. One is in Hueytown and another in Trussville. In short, this is not an easy car to own! A convertible is not fun if it can't be driven. I'd sell it but I am too upside down with it financially. I cannot find anything I like better that is any more reliable. I thought about a Corvette, but my wife dislikes them. Plus, to me, a corvette looks too much like mid-life crisis while the SL looks more like successful attorney.
09-20-2024, 05:12 PM
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I was reading thru some other threads for the battery warning on other SL's and someone mentioned they started using a battery charger when the car wasnt being driven and that solved the issue.
I'm not sure disconnecting the battery will reset any warnings or faults. I think the warning will pop up if the car is currently sensing the issue, as it appears to do in my W204. I'll start the car, put it in drive then as im coasting up the driveway the warning will pop up. Like i said if i pull over, stop and restart the car there is no more warning and it doesnt seem to come back on, until next time i dont drive the car for a few days.
The only reason I bought my car battery from Mercedes is it was actually the cheapest i was finding locally, though I totally forgot about checking Walmart which now I realize they carry them for less than Mercedes and a better warranty by 1yr. Local auto parts stores wanted more money for there agm batteries.
And I do think getting a Mercedes specific OBD scanner is a great investment. You can read and erase the codes yourself. Even before i got the Foxwell scanner i had a $15 basic one and I was able to solve a check engine light on the W204 which turned out to be a faulty purge valve, though i do recommend one specifically for Mercedes so you can do much more with it. I just used my Foxwell scanner earlier this week when I got my car back from a hack shop, now I see they actually installed the O2 sensors in the wrong place, they swapped them, upstream is where downstream should be. Least now I know what needs to be fixed and I bought a new upstream sensor since it looks like they damaged it also.
I was thinking how i would check the transmission fluid level in my W204 with 722.964 if I really needed to. Hook up the scanner and get the trans up to temp, open the drain plug in the transmission pan and see if any fluid trickles out, probably add a quart then adjust the level. If more is needed then add more. You will need a pump and that special adapter to do it. Might as well just drop the pan and change the filter from the sounds of it if you dont think its been serviced in the past. Before ordering everything to do my transmission I went under the car to verify which pan I have, my w204 is right around the age they switched to the deeper pans so I needed to make sure I ordered the right filter. Well I noticed the pan is all rusted pretty bad so ordered a new pan. Then I noticed corrosion on a few of the sprags so I bought all new ones to install. Think i went a bit overboard since I even bought a new bracket that holds the O2 sensor harnesses since mine is all rusted, found a used bracket on eBay in great condition pretty cheap. I found the Shell ATF 134 really cheap on Amazon around $90 for 12 quarts, not sure what type yours takes though. Back to the scanner, one of the main reasons I wanted one was so I can see the transmission fluid temp for servicing it.
I'm not sure disconnecting the battery will reset any warnings or faults. I think the warning will pop up if the car is currently sensing the issue, as it appears to do in my W204. I'll start the car, put it in drive then as im coasting up the driveway the warning will pop up. Like i said if i pull over, stop and restart the car there is no more warning and it doesnt seem to come back on, until next time i dont drive the car for a few days.
The only reason I bought my car battery from Mercedes is it was actually the cheapest i was finding locally, though I totally forgot about checking Walmart which now I realize they carry them for less than Mercedes and a better warranty by 1yr. Local auto parts stores wanted more money for there agm batteries.
And I do think getting a Mercedes specific OBD scanner is a great investment. You can read and erase the codes yourself. Even before i got the Foxwell scanner i had a $15 basic one and I was able to solve a check engine light on the W204 which turned out to be a faulty purge valve, though i do recommend one specifically for Mercedes so you can do much more with it. I just used my Foxwell scanner earlier this week when I got my car back from a hack shop, now I see they actually installed the O2 sensors in the wrong place, they swapped them, upstream is where downstream should be. Least now I know what needs to be fixed and I bought a new upstream sensor since it looks like they damaged it also.
I was thinking how i would check the transmission fluid level in my W204 with 722.964 if I really needed to. Hook up the scanner and get the trans up to temp, open the drain plug in the transmission pan and see if any fluid trickles out, probably add a quart then adjust the level. If more is needed then add more. You will need a pump and that special adapter to do it. Might as well just drop the pan and change the filter from the sounds of it if you dont think its been serviced in the past. Before ordering everything to do my transmission I went under the car to verify which pan I have, my w204 is right around the age they switched to the deeper pans so I needed to make sure I ordered the right filter. Well I noticed the pan is all rusted pretty bad so ordered a new pan. Then I noticed corrosion on a few of the sprags so I bought all new ones to install. Think i went a bit overboard since I even bought a new bracket that holds the O2 sensor harnesses since mine is all rusted, found a used bracket on eBay in great condition pretty cheap. I found the Shell ATF 134 really cheap on Amazon around $90 for 12 quarts, not sure what type yours takes though. Back to the scanner, one of the main reasons I wanted one was so I can see the transmission fluid temp for servicing it.
09-20-2024, 08:58 PM
#7
Super Member
I will buy the battery at a national chain parts store rather than the dealer because I can get a significant discount.
Many swear by a genuine MB battery for the rear- they seem to last much longer and discharge far more slowly.
Your transmission issue is likely a speed sensor in the conductor plate that throws the car into limp.
Blown hoses can be rebuilt for peanuts at hydraulic shops.
I'm not sure disconnecting the battery will reset any warnings or faults.
I'm pretty sure it will, as I've done it several times. Thanks for the W204 input but the R230 has a twin battery system with a sophisticated control module which requires specific knowledge to wrangle. The red warning can be triggered by several things.
Many swear by a genuine MB battery for the rear- they seem to last much longer and discharge far more slowly.
Your transmission issue is likely a speed sensor in the conductor plate that throws the car into limp.
Blown hoses can be rebuilt for peanuts at hydraulic shops.
I'm not sure disconnecting the battery will reset any warnings or faults.
I'm pretty sure it will, as I've done it several times. Thanks for the W204 input but the R230 has a twin battery system with a sophisticated control module which requires specific knowledge to wrangle. The red warning can be triggered by several things.
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09-23-2024, 04:22 PM
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Both batteries installed. The car started right up and everything seemed to be working- but the red light was still on. After testing, I disconnected the negative cables and left them off overnight as suggested by Manning. In the morning, I reconnected them (in the proper order), and when I started the car, the red light came right back on. A local parts store has a scanner and will reset codes- so I will pay them a visit probably tomorrow.ve a unit appropriate for the SL. I cannot drive the car too far until one of the tires is replaced- supposed to be in tomorrow or Wednesday. After that, I will take a nice top-down drive to see what's what.
Another strange thing- in addition to the driver's side door trunk release lever suddenly starting to work for the first time since I have owned the car- now the remote door locks have started working with the fobs! They only work when the fob is right against the sensor on the door (none of this ever worked since I bought the car five years ago). The lights blink and there is a chirp noise. I plan to repair any air leaks affecting the soft close feature with epoxy according to other posts I have seen.
Another strange thing- in addition to the driver's side door trunk release lever suddenly starting to work for the first time since I have owned the car- now the remote door locks have started working with the fobs! They only work when the fob is right against the sensor on the door (none of this ever worked since I bought the car five years ago). The lights blink and there is a chirp noise. I plan to repair any air leaks affecting the soft close feature with epoxy according to other posts I have seen.
