Mercedes-Benz E-Class and E-Class AMG: Why is There a Red Battery Message Saying Visit Workshop?

This article applies to the Mercedes-Benz E-Class and E-Class AMG (2002-2009).

The red battery sign with "visit workshop" message comes on when there is something wrong with your electrical system. When the red battery message appears. you may also notice that the headlights and instrument lights are running dim. There are a number of reasons why you are seeing these symptoms. Your vehicle could be the subject of a. electrical recall or service campaign. You could have a bad auxiliary battery or a bad connection to the auxiliary battery. It could also mean the voltage regulator is not dispersing enough voltage.Fortunately, there are some ways to diagnose the problems before having to take your Mercedes-Benz E-Class to your dealership. Here's what to do when you see that message.

Step 1 – Check VMI (Vehicle Master Inquiry) for updates

Check with your Mercedes-Benz dealer to see if your vehicle has any service campaigns or recalls pertaining to it. Have your VIN ready; the dealer will need it for reference. Sample service campaigns that might affect your car include:

• 2005070017 APR06 alternator E320 (211.065), VIN range A014562-A734487, and X097696-X116123
• 2005060008 JUN06 battery control unit A014562-A418838
• DTP P-B-42.46/84 NOV07 wiring harness, VIN range A040665-A589444

If none of these affect your car, move on to Step 2.

Step 2 – Replace the auxiliary battery

Make sure that the leads to the auxiliary battery are solid and that there is no corrosion that could cause a bad connection. Test the battery to make sure it is putting out 12 volts. If not, you need to replace it.

• Disconnect the negative battery terminal on the main battery before you begin.
• Remove the air filter by unfastening the plastic nut that holds down the air filter; lift the filter off.

• Release the battery hold-down by unfastening two bolts, front and rear, with the ratchet and appropriate socket.
• First, unfasten the negative and then the positive lead to the battery; lift out the old battery.

• Test the new battery with the voltmeter to make sure it is putting out 12 volts.
• If the new battery tests OK, install it into the vehicle.
• Connect the negative and positive leads, re-install the hold-down, and re-install the air filter.
• Start the car and check to see that the red battery and "Visit Workshop" message is no longer there.

If the message is still present, move to Step 3.

Step 3 – Replace the voltage regulator

If the red battery message still shows after installing a new battery that tests well, then the problem could be a bad voltage regulator. In order to replace the voltage regulator, you have to remove the alternator from the vehicle.

• After removing the alternator from the vehicle, place the alternator upside-down on the work bench.
• Remove the plastic cover that hides the voltage regulator from view by removing the two bolts (13 mm and 15 mm).
• Unscrew the three Phillips head screws that hold the voltage regulator in place.

• Install the new voltage regulator, re-tighten the three screws, and re-install the plastic cover.
• Re-install the alternator into the car.
• Start the car and see if the warning message has disappeared.

Featured Video: How to Change the Small Battery on E-Class

Related Sites

• Replace Voltage Regulator - Pelicanparts.com
• Replace Alternator - Pelicanparts.com