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You're reading: What is the purpose of fitting headlight relays?
the wiring size on k100’s was specced to be able to carry the required current on various circuits. it is not large enough to carry additional load (amps) of any significance. the full current is carried by the wiring, through the lh handlebar switch, to the headlight. current = watts/volts, so 60/12=5 amps through the wiring. when you want to increase the wattage of the headlight (for example) the current must also increase, so, say you want to go to 90 watts, then it’s 90/12=7.5 amps, which is 50% more current, so 50% more cross sectional area is required to be able to safely handle that load, the k wiring isn’t up to this task i’m afraid. so, a relay is required. a relay is an electrically operated switch wherby we use the original wiring to operated the relay contact and heavy wiring is used from the source (battery) to the relay and from the relay (load side) to the
world. that way your wiring doesn’t get overloaded like some tosser had done to mine when i purchased it and found a 110 watt globe in the headlight and no relay. how to cook a wiring loom and, if you’re really unlucky, burn your k to the ground. ’nuff said, hope this helps, dennis.