TF24510  24V - 12V   Switch mode Converter
For commercial vehicles, the fitting of this type of dropper is usually preferred.
1)  Find a suitable 24 volt power source capable of supplying 10 amps continuous current.

2]  Connect the Switchmode Converter output + (plus) terminal to the relay terminal +12V. Put a 15amp fuse in this line.
    
3)  Connect 7-core wires follows:
Yellow to relay terminal A
Blue to relay terminal C
Green to relay terminal B
Brown to relay terminal E  (with black)
Red to relay terminal D
Black to relay terminal E  (with brown)
White to to converter output -(minus) terminal
   
    
4)   Connect the thin wires from the relay set to the vehicle's light circuit as follows:
Yellow to LH Flasher
Grey to Fog lamp
Green to RH Flasher
Brown to RH Tail lamp
Red to Brake light
Black to LH Tail lamp
    The thin plain white wire from the relay to a good earth point on the vehicle chassis
5)   Connect the remaining wires of the Voltage Converter as follows:
  • Input + (plus terminal)   to the 24-volt source you identified at step 1. Put a 10 amp blade fuse in this line, as close to its source as possible.
  • Input - (minus terminal)   to a good earth point on the vehicle chassis.     
 
TF24510