Your new stereo will require 3 supplies to switch on
- Ignition live 12v+ red wire on stereo
- Permanent live 12v+ yellow wire on stereo
- Earth/ground 12v- black wire on stereo
- If all these wires are NOT connected then the unit will NOT switch on.
- With the help of a multimeter check to see if you have power at these points.
- Some cars are not equipped with an ignition supply and this is the most common reason for the unit not to switch on. In this case a wire will need to be sourced from another point in the vehicle and connected to the red wire of the stereo harness.
- If there is an ignition wire present, but still no power then check the fuses in the fuse box to make sure that they are not blown.
Most common vehicle with no accessory or ignition live : ALFA ROMEO, AUDI, FIAT, MERCEDES AND VW.