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Could someone please tell me the point of a relay harness in an aftermarket HID kit? My friend and I are having a disagreement on the matter. I think that the relay re-routes the power source from the alternator, directly to the battery....therefore lessening strain on the electrical system and providing steady voltage to the ballasts. My buddy thinks that it's some sort of automatic switch, that you only need in a vehicle without manual headlight controls. I'm not sure where he was coming from on that one. Neither of us are sure of the true answer, but both of us have installed our HID kits with relays and have been satisfied. Could someone that knows the answer please chime in?
 

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I guess it's a tie since you're both wrong, lol. J/K

Usually the point of a wiring harness is that the factory wires going to your lamps are marginal in size. When they are running HIDs typically draw less amperage than standard bulbs, however the ballasts have a fairly high amp draw at startup, like an electric motor. If your wiring is too small then you will get voltage drop when the ballast is trying to light that can cause them to not light properly and/or damage the ballasts over time.

Also depending on the vehicle, if you're wiring was too small and you were running HIDs with a very high amperage requirement, you could draw more power than the wire is rated for causing overheating and voltage drop or in extreme case an electrical fire.
 
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