To relay or not to relay on headlights in my 53 F100 build? (Page 1/1) carnut122 JUL 21, 10:29 AM I'm finally putting the headlights in my 1953 F100 and I thought I had this all figured out, but now I'm second guessing it. I have a major (10 gauge?) wire running from the battery to 2 radiator fans and 1 condenser fan (all about 1 foot in diameter); I don't have a clue how many amps they're pulling. The circuit is on a fusible link and the radiator fans are on one relay and the condenser fan is on another. I was going to pull the power for the headlights from this major power source, but I'm not sure the fusible link can handle it and then I'd have no head lights and no fans. I know the headlight switch is supposed to have it's own breaker in it, but the headlights are 90-100 watt units, so I'm worried about running it through the switch( I don't like the lights to turn off when driving at night). The vehicle has been completely rewired with a generic Painless type of harness. I suspect (haven't looked yet) that the headlight circuit is fused in the fuse box (maybe 30 amps?). The headlight wires (one high and one low beam) seem to be of sufficient gauge. So, now I'm thinking of wiring directly from the headlight switch instead of the battery through relays. Any thoughts? 86FieroSEv6 JUL 21, 07:13 PM If it was me, I would set up a good power distribution block hooked up to the battery with a 4 gauge through an 80 amp maxi-fuse. Then use that dist. block to supply the load feeds of your relays through their own fuses. This way you can use lower amperage fuses from your switches to the relay control circuits. Another helpful item is to set up a gound junction block hooked up to the battery negative and run your grounds to the junction. Clean grounds will go a long way to preserving your old iron and preventing electrolysis and jittery electrical accessories. Make sure to run a good 10 gauge ground from the alternator housing to the ground block as well. Too often I see beautiful power supply with sucko grounding. Remember, every electron leaving the battery must also return to the battery after the work is done. E.Furgal JUL 21, 08:03 PM I'd run the lights with relays.. todays halogen lights draw more current than the engineers figured on.. in the 67-72 c-10 world.. the volts at the light socket, is on ave. 11.9 volts.. changing to relays and the headlight switch only having to switch the relay on/off. the lights get full voltage and are 2x brighter. these trucks the cab main wire+ is tiny.. as back then the load on the system was very low.. wipers/lights and maybe a mono am radio. and heater fan.. doing a junkyard crawl.. a 80's mopar k car.. or any mopar based off it.. the drivers side front strut tower, there is 2 relays and mounting bracket.. just the ticket to add head light relays 1 high 1 low beam.. carnut122 JUL 21, 11:08 PM Thanks for both replies. I decided to go ahead with the relays, and yes, I also need to upgrade my grounds. crashyoung JUL 25, 03:16 PM Use the same gauge for the ground as for the power. Every electron out has to return. Or else you get free heat! Monkeyman JUL 26, 03:38 AM Even the single 55/60w headlight on my bike has a relay (installed by me). The factory wiring (any car/truck/bike) is too small. rogergarrison AUG 11, 07:44 PM You should see the stock sealed beams on my 66 Dodge. There almost yellow and barely light up the road on a dark nite. I cant believe all cars had these headlights in the day. In the sunlight, you can barely tell theyre even on at all. Wiring and grounds are good with new factory harnesses. Its not the bulbs either, all 4 look the same and the spares I have match them too. E.Furgal AUG 12, 08:13 PM quote Originally posted by rogergarrison: You should see the stock sealed beams on my 66 Dodge. There almost yellow and barely light up the road on a dark nite. I cant believe all cars had these headlights in the day. In the sunlight, you can barely tell theyre even on at all. Wiring and grounds are good with new factory harnesses. Its not the bulbs either, all 4 look the same and the spares I have match them too. what is the volts, and amps at the headlight? if it's anything like all the old cars I've had.. it'll be 11 ish volts.. the relays give you full 14 volts to the lights.. and even the stocker T3 lights are twice as bright