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Hi Slick, the relay is used to get full voltage to the lights instead of having the wiring harness rob a small amount, just from electricity having to travel such a long route to the light bulb. Mount 2 relays 1 for hi beam 1 for low beam, putting them as close to the bulbs as is convenient.
Will there be a smaller amp load running 12v headlights? If that's the case, reusing the stock configuration wouldn't be a safety issue, right? I'd like to keep the additional wiring to a minimum. If I have to use a relay I'd like to hide it in the old voltage regulator case. Only thing I'd really be bypassing is the headlight switch.
Higher power requirements. The brighter the more the power draw. You can tell by cautiously touching the switch after the lights have been on for 10-15 min. If it is too hot to touch you need a relay. The better high intensity head lights come with a wiring harness and relay.
Interesting. Most states have a maximum legal limit of 55 watts for low beam, and 65 watts for high beam. Anything more is illegal (if you get caught). I'm running 55/65 watt halogens and they draw the same amount as standard 55/65 watt incandescent sealed beams, save for the milliamp current for the relays. I think what makes the halogens seem more powerful is the color temperature (about 3,800 to 4,100 kelvin). Switching to halogen bulbs is the only legal upgrade you can do according to FMVSS-108. HID and LED headlights are illegal to use period , but not to buy and sell.
Interesting. Most states have a maximum legal limit of 55 watts for low beam, and 65 watts for high beam. Anything more is illegal (if you get caught). I'm running 55/65 watt halogens and they draw the same amount as standard 55/65 watt incandescent sealed beams, save for the milliamp current for the relays. I think what makes the halogens seem more powerful is the color temperature (about 3,800 to 4,100 kelvin). Switching to halogen bulbs is the only legal upgrade you can do according to FMVSS-108. HID and LED headlights are illegal to use period , but not to buy and sell.
Haven't seen anything in the statutes about wattage. The real issue is aim. 300 watt aftermarket bulbs are common but LEDs are changing that. You are right about color temperature. It makes a big difference.
Halogens draw a little bit more amperage than tungsten bulbs but it's not anywhere near enough to matter. If the headlight switch is getting hot or smoked then the actual problem is rust and corrosion in the ground points and harness connections, very common in old trucks. I run a generator and halogens in my slick for almost 20 years with absolutely no problem, but I'm picky about grounding and clean connections.
The relays work slick, the original wiring harness takes a circuitous (heh) route from the battery to the headlight switch, down to the floor switch and then all the way back through the engine bay. Any bulb will have the intensity drop noticeably if the voltage drop is excessive.
That is from the Federal Motor Vehicle Safety Standard 108. FMVSS has had a tough time keeping up with lighting technology changes. SAE has had lots of trouble too. Here is an interesting article from Trucklite that basically says that the SAE standards are recommendations (although the Feds usually follow them), FMVSS takes precedence over state law unless, like in the case of fog lamps, there is no standard so state law rules.: https://www.truck-lite.com/content/n...ng-regulations
Here is the Michigan law that allows 300 candlepower headlights: Michigan Legislature - Section 257.685. Although FMVSS provides min-max candlepower requirements for everyother light on the vehicle it does not for headlights except for stray beams outside of the aim envelope.
So we are getting a bit off topic here. The point here is that many of the legal high intensity lights available cannot go directly through the headlight switch but need a separate relay like the one I got from LMC (#47-3660).
Here is what I put on my truck a couple years ago. I may replace them with LED versions that include park and turn signal as prices come down. LMC #47-0281 headlamps
The relays work slick, the original wiring harness takes a circuitous (heh) route from the battery to the headlight switch, down to the floor switch and then all the way back through the engine bay. Any bulb will have the intensity drop noticeably if the voltage drop is excessive.
Yet many people running relays use a relay mounted in a fuse panel on the inside of the firewall....
It sounds like the OP wants to use stock, 6v wiring on 12v headlights. With half the current, the wiring is oversized. I just don't see any point to a relay system.
