BMW 7 Series: System Components

The Steering Column Switch Cluster as Standard Equipment

The steering column switch cluster (SZL) consists of, among other things, the following components:

• Electronic steering column switch cluster module
• Coil-spring assembly
• Steering-column switch for turn indicators
• Steering column switch for wipers
• Optical steering-angle sensor.

The steering column switch cluster (SZL) can only be replaced as a complete unit. The individual components such as the coil-spring assembly or steering column stalk can not be removed or replaced.

The design and the components of the steering column switch cluster are explained in brief in the following.

Fig. 131: Installation Location Of Steering Column Switch Cluster F01/F02

COMPONENTS DESCRIPTION CHART

1. Steering column switch cluster

Rear View of the Steering Column Switch Cluster

Fig. 132: Identifying Steering Column Switch Cluster Connections

STEERING COLUMN SWITCH CLUSTER CONNECTIONS LEGENDS

1. Connection, vehicle wiring harness
2. Connection for wiring harness in the vehicle (airbag signals)
3. Connection for steering wheel heating/electrical steering column adjustment button block

Optical Steering-angle Sensor

The steering column switch cluster contains the optical steering-angle sensor as well as the associated electronics. A second processor on the underside of the board backs up the information regarding the steering angle and steering-angle speed. This is why the steering angle and steering-angle speed are evaluated and calculated in the second processor in addition to the main processor of the steering column switch cluster.

The steering-angle sensor is designed as a non-contact optical angle measurement system. The system consists of a code disc and an optical sensor. The code disc is connected directly to the steering wheel via a driver. If the steering wheel is moved, the code disc rotates within the optical sensor.

The code disc has a pattern of holes. The pattern of holes is arranged in such a way that four circular tracks are formed. The four tracks represent the digital range of the sensor. The digital code changes when the steering is turned every 0.5º.

Fig. 133: Identifying Code Disc And Optical Sensor

COMPONENTS DESCRIPTION CHART

1. Optical sensor
2. Code disc
3. Hole pattern tracks

Optical sensor

The optical sensor is located on a circuit board soldered onto the board of the steering column switch cluster.

The major components of the measuring system are:

• LED
• Light-conducting element
• Code disc
• Photo-transistors.

Fig. 134: Identifying Photo-Transistors, Code Disc, Light-Conducting Element And LED

COMPONENTS DESCRIPTION CHART

1. Code disc
2. Light-conducting element
3. LED
4. Photo-transistors

LED and light-conducting element

The LED - in conjunction with the light-conducting element - has the task of projecting light from above onto the code disc. The LED is directly soldered onto the sensor circuit board. The light-conducting element is clipped onto the board of the steering column switch cluster.

The light-conducting element is split three ways at the light exit. The light is projected in such a way that a light field is formed at each light exit and beamed downwards onto the code disc. Depending on the pattern on the code disc, light is allowed through or not.

Photo-transistors

There are four photo-transistors below the light exits on the circuit board of the optical sensor of the steering column switch cluster. The photo-transistors detect the optical signals that penetrate the code disc. The phototransistors convert the optical signals into electrical signals.

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