W203 C-180 2007 model (battery drain issue)

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Mbc1802007

New Member
Joined
Sep 13, 2022
Messages
25
Location
Netherlands
Car
C180 2007
Dear All,

In short: I have a battery drain issue under resting condition of about 0.85Amp (850mA). Battery was replaced two weeks ago. I did the fuse test and only fusenumber 57 after removal showed the draw current to 0.65Amp. I do not have memory seat option. Alternator giving 13.6 V on starting for stationary vehicle.

Full story: Trouble started 3 months ago when suddenly I found my car battery dead. I located the cause to be alarm battery which made the blinkers on. Following this, I booked an appointment at an MB dealer which was given almost after 2.5 months. In the meanwhile one day I smell bad from the AC (pee like). Following that I had covid and stayed inside the house for two weeks. The car was flat and will not start (so jumpstarted). I kept noticing that my battery would drain quickly. Red battery sign will appear in the morning while going to work and disappear in the evening while coming back. Finally, went to the MB dealer.

MB dealer found the alarm to be faulty and also replaced the main battery of the car (700 Euro total). After two days, I noticed the red battery sign appeared again and then I immediately took it to the dealer. He re-inspected the vehicle and said that the engine from where the oil goes through needed modification and it was never done on this car. He guessed that this could have damaged the ECU causing the red battery sign. To fix he said anywhere between 2500-3500 Euro (which made no sense for an older car). One of the mechanics at the dealer called me personally and suggested to do the repair with outside garage. Just to double confirm, I do not see any other message at the display apart from red battery sign in the morning.

I went to my usual garage which cleaned up all the excessive oil from all the places and also attached the modification cables. Unfortunately, the very next day the red battery sign was back. Then I did my own test to check the battery drain. I put the car to rest for about 1 hour and checked the drain and it was 0.85 Amp. I removed all the fuses and relays from hood, driving side and the boot (one by one). Except fuse number 57, I found no change in current. After removal of fuse 57, the drain was still 0.65 Amp.

The car drives perfectly, starts perfectly and I have not noticed any other issue as such. Just before this situation, I did change the tires and changed the oils etc.

Any help is appreciated. Thanks a lot.
 
Bump.

Can anyone help this guy before he gets banned for flouting the 30 post rule?
 
My guess would be the alternator. Faulty diodes can cause a drain. I also had a drain, but on removing the alternator and testing the diodes they were fine. But I suspected a fault with the regulator because the voltage displayed in the dash didn't always rise when I started the car. So I changed the regulator and it cured both the intermittent charging and the battery drain. I was surprised, but it seems that it IS possible for the regulator alone to fail in a way that creates a drain.

Your charging voltage of 13.6V seems a bit on the low side. I would suggest testing the diodes, and changing the regulator. I don't know how accessible the alternator is on your engine - it's possible that this can all be done in-situ. In my case I had to remove the alternator, but it allowed me to take it to a specialist to have it checked over and to have the bearings replaced as a precaution while it was out.

PS : @neilrr - I'm new here myself, in what way is the OP flouting the 30 post rule?
 
This is the YouTube video I watched to learn how to test the diodes:
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13.6 volts is too low.
On startup the voltage should quickly reach 14.2-14.3 - maybe a smidge lower if the battery is very flat.
There are 9 diodes in a ‘standard’ alternator. 6 are high current rectifier diodes and three are initial rotor excitation/warning light diodes.
If you are going to test them they should be tested individually. There should be zero current flow in one direction, and in the forward (conducting) direction they should all read about the same -it’s hard to give values as this depends on how much current is flowing. If you are using a dmm, don’t use the ohm scale - there should be an option that will beep and also shows a picture of a diode. This allows a little current to flow in order to forward bias the diode.
My preference is to use an analogue meter but these are getting harder to find.

So, a couple of things. The alternator should put out enough current to at least match the current draw at tickover. When revved up the amount of current produced should easily cover a full load, whatever the state of charge - that is headlights on main beam, heater blower on max, heated rear window on etc etc. this is best measured with a high current DC ammeter (150 amp) in series with either battery terminal or a clip on ammeter (less accurate but MUCH safer) If you slip and actually disconnect the battery while doing this you are likely to blow a lot of electronic kit on the car.
If the charge current looks ok test the voltage regulation.
In terms of voltage regulation, this should be around 14v-14.3. Any lower and you are undercharging. Measure this at the battery. If the voltage is low but the charging current has been ok, suspect the voltage regulator.
If a rectifier diode has failed, it will have failed open circuit or short circuit. Open circuit and the charge current will be low. Short circuit and it can cause a parasitic discharge. You can test this by putting an ammeter in line with the alternator main positive cable. Any discharge will be obvious. Short circuit rectifier diodes often make themselves known by a loud whine from the alternator when under electrical load.
So, if you are confident and can put your hands on the right equipment, the above covers most of what is needed - there are some very unusual circumstances which would confuse the above, but unlikely.
Or find a competent auto electrician.
Be aware that a modern ‘smart’ charging system is a lot more complex and voltages/currents etc shown will not apply.
 
Yes, I don't think the forum platform will allow you to do anything that is against the 30-post rule, so you can't accidentally break the rules. The text that I see at the top of every page (because this is only my 26th post) says:

"Dear ChrisPDuck, You will not be able to use the Private message facility or reply/post to classified threads unless you have a 30 post count. To post a new message please see the sticky post in the new members introductions area. The new members area can be found under General Discussion"
 
He was posting garbage posts - "Thank you. I will try to reach that [edit: the 30 post requirement] asap. 😊" "great!", "Thank you 👍", "Thank you 🙏🏻",, - to pass the 30 post requirement quickly in the mistaken belief his legitimate post about his electrical problem was not visible to the general membership until he had exceeded the 30 threshold.

The 30 post rule applies only to placing ads & sending PMs IIRC.
 
He was posting garbage posts - "Thank you. I will try to reach that [edit: the 30 post requirement] asap. 😊" "great!", "Thank you 👍", "Thank you 🙏🏻",, - to pass the 30 post requirement quickly in the mistaken belief his legitimate post about his electrical problem was not visible to the general membership until he had exceeded the 30 threshold.

The 30 post rule applies only to placing ads & sending PMs IIRC.
Sorry but I do not agree with your first viewpoint. About the second point (mistaken), yes. If some one is saying “welcome”, as a courtesy you say thank you, don’t we? At least I do. Hence, your choice of the wordings i.e. “garbage posts” does not reflect 100% reality.

I would also thank everyone (including you) in this thread who are helping me but now I am confused about moderators’ interpretations so simply holding it back.

Also both PM and ads are/were never my intention.

-Thank you
 
He was posting garbage posts - "Thank you. I will try to reach that [edit: the 30 post requirement] asap. 😊" "great!", "Thank you 👍", "Thank you 🙏🏻",, - to pass the 30 post requirement quickly in the mistaken belief his legitimate post about his electrical problem was not visible to the general membership until he had exceeded the 30 threshold.

13.6 volts is too low.
On startup the voltage should quickly reach 14.2-14.3 - maybe a smidge lower if the battery is very flat.
There are 9 diodes in a ‘standard’ alternator. 6 are high current rectifier diodes and three are initial rotor excitation/warning light diodes.
If you are going to test them they should be tested individually. There should be zero current flow in one direction, and in the forward (conducting) direction they should all read about the same -it’s hard to give values as this depends on how much current is flowing. If you are using a dmm, don’t use the ohm scale - there should be an option that will beep and also shows a picture of a diode. This allows a little current to flow in order to forward bias the diode.
My preference is to use an analogue meter but these are getting harder to find.

So, a couple of things. The alternator should put out enough current to at least match the current draw at tickover. When revved up the amount of current produced should easily cover a full load, whatever the state of charge - that is headlights on main beam, heater blower on max, heated rear window on etc etc. this is best measured with a high current DC ammeter (150 amp) in series with either battery terminal or a clip on ammeter (less accurate but MUCH safer) If you slip and actually disconnect the battery while doing this you are likely to blow a lot of electronic kit on the car.
If the charge current looks ok test the voltage regulation.
In terms of voltage regulation, this should be around 14v-14.3. Any lower and you are undercharging. Measure this at the battery. If the voltage is low but the charging current has been ok, suspect the voltage regulator.
If a rectifier diode has failed, it will have failed open circuit or short circuit. Open circuit and the charge current will be low. Short circuit and it can cause a parasitic discharge. You can test this by putting an ammeter in line with the alternator main positive cable. Any discharge will be obvious. Short circuit rectifier diodes often make themselves known by a loud whine from the alternator when under electrical load.
So, if you are confident and can put your hands on the right equipment, the above covers most of what is needed - there are some very unusual circumstances which would confuse the above, but unlikely.
Or find a competent auto electrician.
Be aware that a modern ‘smart’ charging system is a lot more complex and voltages/currents etc shown will not apply.
@ChrisPDuck and @Ted Thanks for your help.

I did some more tests:
Using voltmeter:
-Battery voltage after charging 12.67V
-Battery after overnight: 12.40-12.55V
-Battery with running engine on 13.5V
-AC current across battery while engine running 0
-AC voltage across battery while engine running 30 mV

Using Console voltmeter:
-In the morning 12.4 V
-0 speed 13.6 V
-running condition 14.4 V

Since I still see only red battery sign and fuses only helped me to figure out 200mA (650 mA still missing), I have following hypotheses :
-One of the diodes is bad in the alternator
-Voltage regulator has gone bad
-Somehow there is a leakage in the alarm system (even though it is new and installed by a dealer)
-Power seat is causing a drain
-Oil leakage has established a bad connection in ECU

I plan today to drive about 40 minutes on a highway and measure the voltage in the battery to see if the battery is charged to 13.2 V or not. Keep you all updated.

Hope it will also some one struggling like me.
 
Since your car electrics are entirely DC, you can forget the AC readings. I think the main thing that stands out from those readings is the low charging voltage of 13.5/13.6V, which most likely indicates a problem with the alternator. If your battery has been on an external charger and then left for a few hours, that 12.67V that you measured indicates that your battery is probably ok, but dropping to 12.4V overnight confirms a drain.

On my car the red battery symbol on the dash indicates an alternator fault. I think in your case that low charging voltage of 13.6V is what's triggering that lamp. So I'm sticking with my earlier suggestion: check the diodes (if a faulty one is found a specialist can replace that for you), and replace the voltage regulator. The regulator is not usually very expensive, compared to a new alternator.

Once you have a properly functioning charging circuit, small drains from things like an alarm or the radio are not usually a problem in normal use, unless the vehicle is parked up for weeks at a time.

*EDIT: One more thing - if your battery has been fully charged on an external charger, your alternator should definitely manage to reach ~14.2-14.4V as long heavy drain items like headlamps are all switched off. If it's still only getting to 13.6V in that situation, it's highly likely that the red battery symbol is telling the truth - there's a fault with the alternator.
 
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Using Console voltmeter:
-In the morning 12.4 V
-0 speed 13.6 V
-running condition 14.4 V
I just noticed this. So your alternator does get up to 14.4V once you're on the move? My own alternator's charging became intermittent - sometimes it would not kick in at start up, so I'd get somewhere around 11.5V to 12V displayed on the dash, but then it might pick up once I started driving. Eventually it reached the stage where it would never kick in. I changed the regulator and that fixed both my mystery current drain and the intermittent charging.
 
I just noticed this. So your alternator does get up to 14.4V once you're on the move? My own alternator's charging became intermittent - sometimes it would not kick in at start up, so I'd get somewhere around 11.5V to 12V displayed on the dash, but then it might pick up once I started driving. Eventually it reached the stage where it would never kick in. I changed the regulator and that fixed both my mystery current drain and the intermittent charging

Yes it goes to 14.4 with rpm. When I just start the car engine and do not press gas then the reading is 13.6 V. But I will defiantly check the alternator. Thank you. I will keep updated.
 
I just noticed this. So your alternator does get up to 14.4V once you're on the move? My own alternator's charging became intermittent - sometimes it would not kick in at start up, so I'd get somewhere around 11.5V to 12V displayed on the dash, but then it might pick up once I started driving. Eventually it reached the stage where it would never kick in. I changed the regulator and that fixed both my mystery current drain and the intermittent charging.
I did the following test:
Drove car on a highway for about 1 hour at night. Before driving, the voltage was 12.3 V (because of Saturday no morning drive). Kept noting voltage while driving. It was more or less 14.5 V. After shutting down the car, I went out and waited for 5 minutes. Then with multimeter noted the voltage. It was 12.7 V.
 
I did the following test:
Drove car on a highway for about 1 hour at night. Before driving, the voltage was 12.3 V (because of Saturday no morning drive). Kept noting voltage while driving. It was more or less 14.5 V. After shutting down the car, I went out and waited for 5 minutes. Then with multimeter noted the voltage. It was 12.7 V.
That seems normal. But the low alternator voltage before you drive away (13.6V) may be the reason that you're getting the battery symbol on the dash - your car thinks it has an alternator fault. As far as I know (and the red battery symbol backs this up), the alternator should provide >14V as soon as you start the engine. But I may be wrong, and it may be that the ECU controls that voltage in your car - 13.6V certainly indicates that the alternator is doing something, so maybe it's not faulty after all.

However, your symptoms are similar to the way my alternator problem developed:
  • A mystery drain,
  • An occasional battery symbol on the dash which led me to monitor the voltage and realise that
  • the alternator was sometimes slow to kick in, but was providing a proper charge once it did. Unlike you though, I got nothing from the alternator - the voltage before it kicked in was 11.5-12V, indicating that it was raw voltage from a battery under heavy load.
After a week or two like this, my alternator became slower and slower to kick in, and eventually it simply wouldn't begin charging at all. I believe this was the voltage regulator gradually failing. I had heard of failed diodes causing a drain, but I hadn't heard of a failed regulator causing a drain. However, in my case the diodes were fine and changing the regulator also cured the drain.

So unless someone else chimes in and suggests that 13.6V is normal in your car, I'd still suggest you change the regulator. It's a cheap part, and if your alternator is readily accessible it's a fairly simple part to change.
 
That seems normal. But the low alternator voltage before you drive away (13.6V) may be the reason that you're getting the battery symbol on the dash - your car thinks it has an alternator fault. As far as I know (and the red battery symbol backs this up), the alternator should provide >14V as soon as you start the engine. But I may be wrong, and it may be that the ECU controls that voltage in your car - 13.6V certainly indicates that the alternator is doing something, so maybe it's not faulty after all.

However, your symptoms are similar to the way my alternator problem developed:
  • A mystery drain,
  • An occasional battery symbol on the dash which led me to monitor the voltage and realise that
  • the alternator was sometimes slow to kick in, but was providing a proper charge once it did. Unlike you though, I got nothing from the alternator - the voltage before it kicked in was 11.5-12V, indicating that it was raw voltage from a battery under heavy load.
After a week or two like this, my alternator became slower and slower to kick in, and eventually it simply wouldn't begin charging at all. I believe this was the voltage regulator gradually failing. I had heard of failed diodes causing a drain, but I hadn't heard of a failed regulator causing a drain. However, in my case the diodes were fine and changing the regulator also cured the drain.

So unless someone else chimes in and suggests that 13.6V is normal in your car, I'd still suggest you change the regulator. It's a cheap part, and if your alternator is readily accessible it's a fairly simple part to change.
Today I noticed an interesting result. Before going to office, I checked the voltage and was expecting about 12.1 (since last night it was 12.3). To my surprise it was 12.7. Not sure how did it increase on its own.

Another interesting result was that the voltage as displayed in the console for a few second was 16.2V and soon it displayed red battery sign.

Now Is there a connection or I am just establishing it ?
 
Today I noticed an interesting result. Before going to office, I checked the voltage and was expecting about 12.1 (since last night it was 12.3). To my surprise it was 12.7. Not sure how did it increase on its own.
When the battery is under load it may show a lower voltage, so it's possible that some of your car's systems were still powered when you measured 12.3, but they had gone to sleep by the time you measured 12.7.
Another interesting result was that the voltage as displayed in the console for a few second was 16.2V and soon it displayed red battery sign.
16.2V is too high - more evidence that your voltage regulator is faulty I think.
 
When the battery is under load it may show a lower voltage, so it's possible that some of your car's systems were still powered when you measured 12.3, but they had gone to sleep by the time you measured 12.7.

16.2V is too high - more evidence that your voltage regulator is faulty I think.
Just to give you and others an update, last week, I took my car to a local garage to specifically look for the drain. They kept the car for week, checked the alternator and it was at one point giving 11 V. The car was kept for a week because they put overhauled alternators and two of them were found faulty upon replacement.

Now the alternator has been changed. They said that the drain should be gone. They did not guarantee but said that there could be other causes of drain but first check the car with the new alternator.

So I have brought back the car and keeping it under observations. Will update.Fingers crossed.
 

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