General Information

Workshop Hints

Battery Disconnect Switches
All BMWs arrive at the center equipped with a battery disconnect switch. The purpose of the switch is to allow an easy way to disconnect the battery circuit when the vehicle is not in use. Disconnecting the battery allows service intervals to be extended to 3 months on vehicles which are in storage.

There are two types of Battery Disconnect switches:
- Mechanical
- Electronic

Mechanical Battery Disconnect Switch







The mechanical switch is connected to the negative ground point of the battery and come in various lengths.

At the end of the switch is a large red plastic key that is used to interrupt the battery ground circuit.

The battery disconnect switch should only be left in if the vehicle is to be placed into storage. After the vehicle is parked the switch can be turned off.

Under no circumstances should the vehicle be delivered to a customer with the battery switch still installed, it should be removed during the second half of the QC I.

If the vehicle is to be used as a demo. or put into Loaner Car service, the Battery Disconnect switch should be removed during the initial check.

When the switch is removed from the vehicle it should be returned to the Parts Department where it can be shipped back to BMW to be recycled in another vehicle.

Electronic Battery Disconnect Switch (EBS)
Since 2000 a new battery disconnect switch has begun to replace the mechanical type. The purpose of the switch remains the same as the mechanical type, so does the criteria for removing it or leaving it installed. There are two types of electronic switches, magnetic or a rocker switch.

The Magnetic EBS kit includes:
- Magnetic pen with holder
- Magnetic sensor with cable
- Electronic Battery cable







The non-magnetic type uses a rocker switch instead of the magnetic sensor.

The magnetic pen is used to turn the magnetic switch on and off. It is usually attached to the lower left corner of the windshield.

The magnetic sensor with connecting cable is installed inside the vehicle and attached to the drivers sun visor bracket mounting points (1).







The rocker switch type is usually draped over the rear view mirror. The connecting cable plugs into a connector for the signal line which is routed to the battery area. The signal line wiring is a permanent part of the vehicle wiring and is not removed.

To connect or disconnect the battery, flip the rocker switch (LED off) or hold the magnetic pen in front of the sensor.

When the pen is held in front of the "Off" sensor the LED will turn off. The battery is now disconnected.

Status of the switch is as easy as viewing whether the LED is on or off from outside of the vehicle.







The procedure to remove the Electronic Battery Disconnect Switch from the vehicle is the same for both switch types:







1. Disconnect the negative terminal of the battery.
2. Disconnect the two nuts from the bolt connections (2) on the BST and remove the electronic disconnect switch.
3. Disconnect the 3-pin plug connector (1) between the electronic switch and the harness connector of the signal line. The signal line wiring remains in the vehicle and the connector should be taped back to prevent rattles.







4. The location of the 3-pin connector will vary according to vehicle (1). Disconnect the sensor from the connector and secure the signal line back to the main portion of the harness and store it out of sight (2).







5. Remove the rocker switch and harness or the magnetic sensor and install the sun visor holding bracket if necessary.
6. Remove the magnetic pen holder from the windshield and return all components back to the Parts Department.