hello, my friend just bought a pair of 100/130 watt headlights for his 96 cavalier. he bought them over the internet and the guy told him that he should run a relay for the lights and not use the factory wiring. but he never included any information. i know how to use a relay and wire them up. i'm just confused on what wires to run to the relay. or would he be able to run those headlights off his stock wiring?
Yes, it'd be a good idea to use a relayed harness to relieve the strain on the factory wiring. However, I'd try to persuade your buddy away from something this high powered in a factory headlight assembly. You could probably use 80/100 watt bulbs with no adverse affects. The problem herein lies with the extra heat generated- especially with colored bulbs (blue, etc.) All the extra heat can actually fade the reflective surfaces inside the assemblies. The headlights will start out much brighter, but will be probably dimmer than stock in the end- it's happened before.
You could make a relayed harness yourself using the factory harness to trigger your relays. You may also want to research an HID headlight upgrade. I could go on, but it'd be easier to point you here: https://faqlight.carpassion.info/
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My ex once told me I have a perfect face for radio.
I agree with geepherder. Besides being too hot for the plastic assemblies and causing peeling, they also can actually cause melting too. Another reason to stay away is that the housings & lenses are only effective up to a certain amount of light, and anything more may not be 'controlled' properly by them. Depending on what he needs the extra light for, he may either want driving lamps (to supplement the high beams) or auxilary low beams.
In regards to lighting in general, I recommend relays and larger wiring for all headlights etc. The OEMs are pretty skimpy on what they put in. I have seen several vehicles where the lights are actually brighter with just the changeover to larger wiring and relays.
Basic headlamp relays- 1 for low, 1 for high
30 battery
85 ground
86 to factory headlight wiring
87 to headlight