Home > Troubleshooting > Electrical Problems > BATTERY/ALTERNATOR VISIT WORKSHOP DIY


Typically you get a BATTERY/ALTERNATOR VISIT WORKSHOP warning when the electrical system voltage in the car is below 12.6 volts. When the car runs, the alternator produces electricity, and the voltage should be above 13.5 volts. If you have a multimeter like this, you can connect it to the battery terminals to get a voltage reading.


  1. The main battery is near the end of its life.
  2. Alternator problem
  3. The secondary (Aux) Battery needs replacing (if applicable). 
  4. Loose or lousy battery terminal connection.

battery malfunction

Just because you can start the car in the morning doesn’t mean your main battery is in good condition. The battery may be near the end of its life and doesn’t provide the necessary. Check the main battery before starting the car if you have a voltmeter. It should have about 12.5 volts. If it is lower than 12, you need a new battery.
Here is a simple test you can perform if you get Battery Defective message at start-up. Let the car run for about 10 -15 minutes. Then turn off the car, make sure all the lights are off, and nothing is on for 30 seconds. Then start your car back up again. Do you still get the Battery Defective message again? If you don’t, your main battery is not holding a charge properly, especially if the car has been sitting for a long time. You will be ok to drive the car but replace the battery as soon as possible before it does not last very long.  Mercedes uses battery group 49, and if you want to save some $$$, you can get an AGM battery, which the dealer uses for less on Amazon. Here is a highly rated battery on Amazon that will fit Mercedes Benz cars.
More often than not, the real problem is the voltage regulator in the alternator. You can replace just the voltage regulator if you know the real problem. Otherwise, it would be best if you replaced the whole alternator. Before replacing the alternator, ensure your battery is not the problem. Go to Advance Auto Parts or AutoZone to troubleshoot your car and have them do a FREE alternator/battery check. This test may be able to point you in the right direction.
Some Mercedes Benz models, such as the E or CLS Class, have a secondary battery. This is a smaller 12-volt auxiliary battery that is used as a backup. The system also checks this battery’s voltage; if it is lower than 12.6 volts, you will get the error on your dashboard. So if you replaced the main battery and were wondering why you are getting the Battery/Alternator Visit Workshop message, check this battery as well. Before you start the car after sitting for a few hours or overnight, grab a multimeter and check the voltage at the secondary and the main battery. If you have less than 12.5 volts at either one, you know your problem. You can get a multimeter for testing on Amazon for about $20, and they are very easy to use even if you have never used one before. For example  this one, 
4. Battery Terminals
This may sound like to obvious, but it was driving me crazy one time on an E Class. I was getting the Battery Visit Workshop message and knew I had good batteries. The negative post’s battery terminal was loose, causing this problem. You can remove the terminal connections and clean them up just to be sure. I use sandpaper around the terminal post and at the cable end connection to clean up.
These are the main reasons you get the Battery Alternator Visit Workshop Error Message. If you need to replace any of the batteries, you can order them on Amazon using the links below and also help us at the same time.
Malfunction electrical consumers switched off.
You may get Electronic Consumers switched off when the car’s computer has detected a low voltage. This happens when the main battery is old and goes wrong. Test the main battery and replace if defective.

Before troubleshooting, you must know if your car has one or two batteries. Why do some models have two batteries?

According to Mercedes-Benz, the main battery, usually found in the trunk, supplies the onboard electrical system in regular operation. While the secondary (auxiliary battery is a short-time backup for the power supply in the event of the onboard system battery failing. E Class W211, CLS Class, for example, has two batteries. 

The sequence of the electrical system:

• The battery control module monitors the operating states and the vehicle’s voltage conditions.
• Depending on the performance measured for the battery, consumers can be switched off in 2 priorities (switched off using CAN message). In this case, you may get an error message:
malfunction electrical consumers switched off. Check your batteries and alternator. 
• The battery control module (BCM) activates the battery isolating relay (K57/2) if necessary. A distinction is made between 2 states:
– recharging of additional battery
– engaging additional batteries in critical on-board network situations

N82 Battery control module (BCM)

The battery control module is installed in the trunk to monitor the batteries (the installation position depends on the equipment. Minispare/full-spare wheel or Tirefit).

The tasks of the battery control module are:
• Detecting the battery state
• Switching off consumers (energy management)
• Connecting the additional battery if necessary (through the battery isolating relay K57/2)

What Scanner Can I Use to Troubleshoot Mercedes-Benz Alternator Problems?

If you’re experiencing problems with your Mercedes-Benz, a YOUCANIC full system diagnostic scanner can help you troubleshoot the issues. This advanced diagnostic tool can read and interpret the fault codes stored in your car’s computer system, providing detailed information about any problems with the engine, transmission, brakes, or other critical systems.

The YOUCANIC scanner can also perform diagnostic tests on various systems, including the ABS, airbag, and steering systems, to help pinpoint the root cause of any issues. With this information, you can make more informed decisions about repairs and maintenance, saving time and money on costly repairs.

If you have any questions or comments, please post them below in the comments section. 


  1. I have c320 model c320 my belt was broken and sign was alternated and power steering not working then I buy new belt and fix it and driver my car two days very good but after that I think my son leaves the lights o that’s why in the morning I try to start but nothing curent I try with jump leads other car but didn’t start and sign on meter restarting system visit workshop .some one can tell me what I do for it

  2. My 2002 Mercedes c 180 w203 Petrol was showing battery visit workshop. This got me worried, I bought a new battery and this did not fix the issue. I call an electrician to check the alternator, change the cutout and check the brush if they were okay. Just to notice that the CUT-OUT was faulty after replacing it the problem is now solved.

  3. The positive wire from alternator to starter has got a 175amp fuse. Usually that one is the culprit

  4. I have an 02 Mercedes Benz E320 4matic. I got the battery/alternator light on the dash and checked the main battery to see the voltage and it wasn’t 12.5 not running. When it is started the voltage seems to go down and I took the alternator out and had it tested at advanced autontoday and it read the alternator is good. If just the regulator is bad, I’m at a loss. I don’t know if my year has a secondary battery. I’ve looked all under the hood and took things apart and don’t see one anywhere. Any feedback is greatly appreciated

  5. A problem that i have with My w211 E-Class 220 CDI from 2005 . I was driving one day from home to go to a restaurant when my car entered in some kind of ” LIMP MODE ” that resulted in my car standing still, not moving at all. Before my car switched off completely, the radio went on hi volume for 1-2 seconds, all the dashboard lights lighted up (like a Christmas tree) and after that it stopped completely. (dashboard black, engine stopped and the ignition ” dead”) . After few minutes i put the gear box in P mode and give it a go: it started but a message saying ” battery convenience functions temporarily unavailable ” was on the dash of the millage and nothing else was going : A/C, Radio, Chairs … When one of my friends put his car diagnostic laptop on my Mercedes, the following errors where found : Battery Energy Control Module – BSG211 (battery energy control module 4 fault codes) : 9051 Consumer shutoff, stage 1 Intermittent; 9050 Consumer shutoff, stage 2 Intermittent; 9092 Auxiliary battery Intermittent; 9071 Auxiliary battery relay Intermittent.
    Also i managed to identify and change the auxiliary battery that was the original Mercedes Benz , and on it had the code 34 04. Another thing that i noticed is the fact that on Delphi (the diagnostic software used to diagnose my car ) there is an identification code for the BCM: MB 2114420155. This code i think that is used when you want to change a faulty part but on my physical BCM that i have in the trunk there is another number and there is a wire that doesn’t go from the harness (it seems to be some kind of improvisation made before i bought the car)

  6. I have a 2003 e320 i once had the red battery sign fixed it by putting a new alternator worked fine with no red battery sign for 2 weeks then again the same red battery problem? I have a new main battery nd a new alternator. Idk if i could have a draining problem or something is hurting my alternator because it was fine for 2 weeks only till the same problem came again.

  7. Hi there, I have a problem with my 2006 c class 180 Kompressor. Recently the battery/ alternator not charging light has been coming on had the battery checked at garage they say it’s fine they put it on their diagnostic test which came up which 2 charge faults, car sometimes goes into limp mode and shuts everything down. Just checked the output on the dash readout which says 12.3 do you think it could be the alternator.

  8. Hello I have a 2012 c250 I know I only have the main battery and not an auxiliary battery in the car…..I am getting the battery symbol that comes on then I get a message saying COMMAND SHUTTING OFF and navigation ….radio and all that turns off but car stays on for a while before it just completely shuts down…..I took battery to O Reily because the battery was dead but they were able to charge the battery back up….do I need to replace battery completely or is it the alternator ??? Please help

  9. I have a 2004 E320 wagon 4matic, suddenly while driving it loose power the passenger headlight start flashing like it give you a code the inside light started flicker as well, take it to a shop they said the alternator is not charging go ahead and replace it, it’s charging now but the cooling fan is racing the right front headlight still flashing as well as the interior. Replace the small battery after being test bad, replace BCM, replace passenger footwall junction fuse or pre-fuse block, replace alternator three times, replace left front SAM and left rear SAM still same problem at this point I am out of option it look like I’m rebuilding this car, I check all the ground and positive cable, at idle it give 11.9 to 12.2 if I rev the engine it will go to 13.3 but no red battery light’s on.

  10. Hi. I have a 2002 mercedes c240. The alternator failed in march ’17 and i replaced it. In June ’17,same issue and changed the alternator again. Today it started showing the same bad battery/alternator error. The output i am getting is only 11.8Amps.
    Please advise if the only option is to it take to the dealership or i can check anything else also.

  11. Hi. IHave a C230 Kompressor Coupe with 271 motor. I replaced the motor and now the Computers is coming on red indicating “Alternator/Battery visit workshop”. Alternator charges perfect and battery replaced.. Car does not pull very good? Terminals replaced.

  12. We have a 2011 ML350 4Matic. Car would sometimes start and sometimes not. Had a new alternator installed. Next day the car would not start. Had new battery installed. Started, no problem. Few hours later, would not turn over at all. After several attempts, car would finally turn over. Happened 3 or 4 times during the day. No warning lights or messages come on. What could be the problem?

  13. Hello, I’ve got a tricky “Visit workshop!” issue on a 2003 E55, and hopefully you can offer some hints to track it down.

    When I start the car cold, its completely fine. 75-100% of the time when I start the car warm/hot I get the “Visit workshop!” error with the battery icon. I replaced the BCM and the front pre-fuse box in the passenger footwell, but neither helped.

    The alternator is putting out good voltage, and a digital battery charger with an on-board alternator test said its Good.

    DAS shows error 9055 in the BCM and ECU: “The terminal 61 signal on the CAN bus is missing or is faulty.” The ECU has a guided test for this, and shows terminal 61 is OK. I looked up the diagrams and it appears that this is a 2-wire connector from the Driver-side SAM to the voltage regulator. The harness and wire seems fine on both ends.

    At this point I’m not sure where to go next. Considering replacing the alternator, replacing the SAM, or running new wires for terminal 61.

    I’ve seen references to component F56 “Starter, alternator fuse (in wiring harness)” and that it could be the problem, but I can’t find this component. I even purchased a used cable and took it apart, nothing there but thick wire. Also, this wire seems impossible to replace without pulling the motor since its on a bracket which is attached to a bellhousing bolt and there is no space to get a torqy tool in there.

    Thank you!
    Mike K.

    • That is definitely tricky and not normal. As I read you post can’t help but think that this may be a loose contact in the charging circuit or a bad ground. The terminal 61 may be the issue as well. It may test fine when you are doing the test but that doesn’t mean that it can’t be a loose contact and acts up at random.

    • The positive wire from alternator to starter has got a 175amp fuse. Usually that one is the culprit

  14. something is draining my main trunk battery on my 2005 E320 v6 gas sedan
    I removed all fuses front and back to pinpoint and I still had the drain…
    I do not have any warning lights or messages,
    now I am considering installing a battery cut off to keep the battery charged
    so I can start the car when I want with no problems.
    Is there a negative effect to this solution?

    • You will loose the sync function of seats, windows, sunroof and radio every time you cut power like that. Other than that it shouldn’t effect anything when you do this a few times. That doesn’t mean that doing this over and over again couldn’t result in unpredicted effects.

      Check for a current draw one more time. You may get lucky this time. It has to be one of the circuit protected by one of the fuses.

  15. I have a e350 mercedes benz the battery/alternator light was on..I had the battery checked; it was weak..I got a new battery..the light still comes on but it doesn’t stay on..comes on and go off in spurts….i have one battery in the trunk…

  16. My 2003 mercedes e w211 diesel is showing battery visit workshop . Even i changed the battery . The problem is when we start the car it will be fine showing the malfunction after running of 20 mins it gets suddenly switch off showing ignition light’s

    • This can be tricky to diagnose. It may be something as easy a bad ground. You will need to connect your car to a diagnostic scanner to get a better idea what is causing the error message.

      • Hi, I get the battery error on clk270cdi after driving for 30 minutes, usually under acceleration, braking or hard turns – in my oppinion things that will put some stress on the car.

        I have icarsoft MB2 and the errors I get are :p1664-002, p1129 and b1115.

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