Circuit Operation - Steering Wheel Controls

The steering wheel controls consist of two components:
^ Steering wheel control switch
^ SIR Coil Assembly

Steering Wheel Control Switches
The steering wheel switches control both Radio and HVAC functions. These switches are actually a ladder network consisting of the switches and a series of resistors.

The ladder network is arranged so that each switch has a different resistance. This allows a different voltage output to the radio for each switch pressed.

SIR Coil Assembly
The SIR coil assembly contains four wires used by the steering wheel controls. This allows voltages to be sent from the steering wheel switches to the radio while the steering wheel is being turned.