55.2-59 Wiring Advice - Headlight relays with new harness?

[59chev]

I am starting to plan the wiring part of my build. I have removed every piece of original wire and have a Haywire E-Series Kit that I will be installing. The Haywire kit comes with 14 Gauge wire for the headlights.

My question is with all new wiring should I think about adding relays for High and Low Beam while I am at it? Alot of the articles I have been reading about upgrading to a headlight relay kit was to fix a problem of dim headlights due to the fact that the original wiring was undersized and likely old and brittle. With brand new wiring are the relays needed? I plan on just running sealed beams for now.

Second question: Where should the headlight switch get battery power from? I know that the switch itself has a circuit breaker in it so I don't think it should be fused.

- The ignition switch?
- Tap into the main power for the fuse block?

Thanks!

[MiraclePieCo]

Complete wiring kits from major manufacturers like Haywire have completely adequate circuitry - I have never needed to add supplemental relays. Simple is better; any additional wiring, relays and connectors are just more places for wiring to fail. If lights are dim, 99% of the time it's an inadequate ground.

Your fuse block should have a hot wire power for the headlight switch. If not, you can add one.

[jwhotrod]

the answer is a little more complicated then the above. If you intend to go to halogen headlights, or something similar, they are typically high amperage draw (25-35A) that puts a significant load on a "stock" headlight switch and can get same VERY hot, to the point of melting. in that case or if you just want to take some of the load off the switch install a relay.

[mr48chev]

Originally Posted by jwhotrod

the answer is a little more complicated then the above. If you intend to go to halogen headlights, or something similar, they are typically high amperage draw (25-35A) that puts a significant load on a "stock" headlight switch and can get same VERY hot, to the point of melting. in that case or if you just want to take some of the load off the switch install a relay.

Pretty word for word what I was thinking. If you plan to run something more than off the shelf at the parts house Halogens you want relays to protect your switches. The regular GE, Sylvania or Phillips halogens don't draw that many extra amps over a regular seal beam headlight but if you are running lights that use an H-4 bulb that may be 55/100 that is too much draw to put though the headlight and dimmer switches. I burned out a lot of dimmer switches in my 71 GMC before I put relays in.

[joedoh]

Originally Posted by jwhotrod

the answer is a little more complicated then the above. If you intend to go to halogen headlights, or something similar, they are typically high amperage draw (25-35A) that puts a significant load on a "stock" headlight switch and can get same VERY hot, to the point of melting. in that case or if you just want to take some of the load off the switch install a relay.

exactly, agreed. and I will add to mr48s comment about dimmer switches that usually adding a relay is done so you can get the ~14v in a super short path from the alternator output to the lights instead of ~12.whatever you have after running through all the connections including the high current contacts in the headlight switch. In older cars I used to do this and the lighting difference was very noticeable.

[59chev]

Thanks for the feedback guys! Gives me lots to think about as I plan out my wiring.

[59chev]

I have a spare circuit in my new fuse block for Power Seats. It is has a 30 Amp fuse and 12 Gauge Power wire. Since I know for certain that my truck will never have power seats, could I use this to power a High Beam and Low Beam relay for the headlights? If I'm reading the wiring schematics correctly, only one or the other relay would be powered up at a given time, not both. I would mount the relays under the dash next to the fuse block and run the new 14 Gauge High and Low Beam wires up to the headlights from the relays.

[jweb]

Originally Posted by 59chev

I have a spare circuit in my new fuse block for Power Seats. It is has a 30 Amp fuse and 12 Gauge Power wire. Since I know for certain that my truck will never have power seats, could I use this to power a High Beam and Low Beam relay for the headlights? If I'm reading the wiring schematics correctly, only one or the other relay would be powered up at a given time, not both. I would mount the relays under the dash next to the fuse block and run the new 14 Gauge High and Low Beam wires up to the headlights from the relays.

If you're going to add relays, just use the circuit intended for the headlights.
Here's a video that shows how to wire in the relays.

https://www.youtube.com/watch?v=bcY2CG07wi0

[59chev]

Thanks for the link. The reason I was considering using this circuit is the Headlight switch itself still needs power to trigger the relays. My thought was to use the wire intended for the Headlight circuit to power the Headlight switch and use the unused “Power Seat” circuit to power the relays.

[jweb]

When you add relays the power needs to come directly from the battery or alternator.

I can't remember the wire gauge used but is larger than 12.

I can't find a Haywire harness diagram but you can see in the link the EZ wire diagram has a red/black wire for the switch (that doesn't change). On this harness you would add the relays on the Lt. Green and Tan wires that are shown for the headlight plugs.

http://d44tech.com/EZ_Wiring_Manual.pdf

[duramax55]

on my truck i put the relays up front close to the head lites then you only have to run small triger wier to the relays. all you need is a 16 guage wier