The incorporation of a Hella relay is essential to obtain the maximum operating efficiency of all lighting and signalling equipment. Relays prevent voltage drop accross switches and wiring which have inadequate current carrying capacity. 

A vehicle's switches and wiring are only inadequate for lamps and horns fitted as original equipment. Overloading will occur with the fitting of additional lamps and horns, causing voltage drop. By fitting a relay you will maintain full voltage and ensure maximum performance.

The table illustrates the significant reduction in light output experienced due to voltage drop. This is based on a mean operating voltage of 100% = 13.5V or 27V.