Double-DIN stereo installation — loose wires explained (blue, green and purple)

When installing a double-DIN stereo, there may be loose wires in addition to the power and speaker connectors. These are used for functions such as amplifiers, antennas, reversing cameras and steering wheel controls.

Wire colours may differ between stereo models. Always check the wire’s label and the stereo’s installation manual before connecting it.

What do the different wire colours mean?

Example colour	Common label	Function
Blue/white	P.CONT / AMP REMOTE / SYSTEM REMOTE	Controls turn-on of an external or factory amplifier. On some stereos, it can also control the antenna.
Blue	ANT.CONT / POWER ANTENNA	Controls a power antenna or antenna amplifier via the correct connection or adaptor.
Light green or green	PARKING BRAKE / PRK SW	Detects whether the parking brake is applied.
Purple/white, sometimes purple	REVERSE / BACK	Receives a reverse signal so the stereo can switch to the reversing camera image.
Light blue/yellow	STEERING WHEEL REMOTE INPUT	Used for steering wheel controls via a compatible adaptor interface.
Pink	SPEED PULSE / VSS	Receives the vehicle speed signal on stereo models that use it.

Please note: Green and purple are also used in speaker wiring. Never identify a wire by colour alone.

Should blue and blue/white wires be joined together?

Not automatically. Antenna control and amplifier remote turn-on can have different functions. Some stereos have a shared output; others have separate connections.

Follow the stereo and adaptor harness manuals to choose the correct output. Remote is a control signal, not the amplifier’s main power supply.

How do I connect the parking brake wire?

Connect it to the car’s parking-brake-applied signal according to the stereo’s installation instructions.

Some features or settings may require the stereo to detect that the parking brake is applied. The relevant features depend on the stereo model.

How do I connect the reversing camera wire?

The wire labelled REVERSE or BACK receives a signal when reverse gear is selected. This switches the display to the camera image.

Connect it according to the stereo and any adaptor harness manual. The reverse signal is separate from the camera’s video signal and power supply, which must also be connected correctly.

Do all loose wires need to be connected?

This depends on the stereo, car and required features. Check the manual for necessary connections.

Insulate unused wires individually so they cannot cause a short circuit.

Which adaptor harness do I need?

The harness must suit the car model, model year, original equipment and new stereo. It may be needed to retain steering wheel controls or activate a factory amplifier, for example.

If you need help, provide these details and a clear photo of the connectors and loose wire labels.

Switching on the factory amplifier (remote)

The two illustrated adaptor examples use blue control wires to switch on the factory amplifier. Connect these to the stereo harness’s appropriate remote turn-on output, confirming the labels and manuals rather than relying on colour alone.

Active system adaptor

Steering wheel control harness

Controlling a power antenna or antenna amplifier, if fitted

Some cars have an antenna amplifier in the roof or door mirrors. Its blue control wire needs the appropriate connection to switch it on. This is common in vehicles from brands including VW, Audi, Seat, Skoda and Citroën. Confirm the correct output using the stereo and adaptor instructions.