Headlight Relay Mod

[JamesDEvans007]

I have searched and came up dry on finding a schematic for the Headlight relay install. I know I can buy a pre made harness, but I have several relays and plenty of wiring/connectors and such to build my own. Just need to know how on the 4 light system.

 

[89Suburban]

Why you running relays? Increasing the load?

 

[JamesDEvans007]

No. Atleast not yet. I want to pull juice from the battery instead of the headlight switch...less voltage drop equals brighter lights. Future plans of HIDs also, and they like steady current. Yes they draw less power once on, but HIDs pull more when first turned on...on the startup surge.

 

[Alaskaskiff]

This is normally done to decrease the voltage drop to the bulbs, which increases headlight output. Just think of it this way, you are using the old circuits as the triggers for the relays. Main power from the relays come from the battery and goes out to the bulbs.

 

[89Suburban]

Nice, I never thought about it like that. Got my attention.

 

[JamesDEvans007]

Nice, I never thought about it like that. Got my attention.

Like Alaska said, a quick way to verify drop is to take a voltage meter and measure. At the output terminal on the alternator, the battery, on the fuse panel, and also at the headlight plug.

I moved the voltage sense wire to a open batt connection in the fuse block and changed the voltage drop from the alternator to the fuse block from .87 volts to around .17. Alternator now senses from the load side of the fuse panel instead of the charge lug on itself. The sense wire is normally looped from the 2 prong plug on the alternator back to the charge lug.

I also upgraded the big 3 with 4 guage wire, and ran the charge wire from the alternator directly to the battery.

 

[JamesDEvans007]

If and when I do upgrade the lows to HID, I can't think of any way to keep the lows on with the highs without using a one-way diode or put in a third relay. That is because the upper bulbs are high and low beam. I want to keep all 4 lights on when the highbeams are on. Anyone have any other ideas....I'm open to suggestions

 

[89Suburban]

Like Alaska said, a quick way to verify drop is to take a voltage meter and measure. At the output terminal on the alternator, the battery, on the fuse panel, and also at the headlight plug.

I moved the voltage sense wire to a open batt connection in the fuse block and changed the voltage drop from the alternator to the fuse block from .87 volts to around .17. Alternator now senses from the load side of the fuse panel instead of the charge lug on itself. The sense wire is normally looped from the 2 prong plug on the alternator back to the charge lug on it.

I also upgraded the big 3 with 4 guage wire, and ran the charge wire from the alternator directly to the battery.

Damn. I got to remember this.

 

[notverrysmart]

If and when I do upgrade the lows to HID, I can't think of any way to keep the lows on with the highs without using a one-way diode or put in a third relay. That is because the upper bulbs are high and low beam. I want to keep all 4 lights on when the highbeams are on. Anyone have any other ideas....I'm open to suggestions

http://www.gmt400.com/forum/archive/index.php/t-122.html there is a link for the 4 hi headlight mod for a gmt400 truck.
as for the HID upgrade, I havent really messed with them too much yet but my understanding of them is the ballasts get a turn on signal from the original headlight harness (the voltage that would turn on your halogen bulbs) so in theory if the low beam halogens would stay on when your highs are on then with HIDs it should still do the same.

Edit - because we have designated bulbs for high and low beams, unless you wire the HIDs to switch to their high beam they should stay in low. Im gonna go smoke and ill snap a couple pictures to support my theory

Bah teach me to think, we do have a 3 prong for the lows so you are right about the diode
both connectors, you can see here that the high beams have 2 wires black (ground) and green (hot)

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low beam connector you can see the black, green, and orange

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so with this my thought would be put diodes on the green and orange both feeding into the low beam of the ballasts and the HID will stay lit up when you click your high beams on.

 

[JamesDEvans007]

http://www.gmt400.com/forum/archive/index.php/t-122.html there is a link for the 4 hi headlight mod for a gmt400 truck.
as for the HID upgrade, I havent really messed with them too much yet but my understanding of them is the ballasts get a turn on signal from the original headlight harness (the voltage that would turn on your halogen bulbs) so in theory if the low beam halogens would stay on when your highs are on then with HIDs it should still do the same.

Edit - because we have designated bulbs for high and low beams, unless you wire the HIDs to switch to their high beam they should stay in low. Im gonna go smoke and ill snap a couple pictures to support my theory

Bah teach me to think, we do have a 3 prong for the lows so you are right about the diode
both connectors, you can see here that the high beams have 2 wires black (ground) and green (hot)

You must be registered for see images attach

low beam connector you can see the black, green, and orange

You must be registered for see images attach

so with this my thought would be put diodes on the green and orange both feeding into the low beam of the ballasts and the HID will stay lit up when you click your high beams on.

Yeah, 3 wire on the upper bulbs. The HID install is pretty easy and straight forward. I've done it on a few other vehicles, mine and friends. Plug and play on newer vehicles, I just stress putting in a relay to power them.

 

[notverrysmart]

Yeah, 3 wire on the upper bulbs. The HID install is pretty easy and straight forward. I've done it on a few other vehicles, mine and friends. Plug and play on newer vehicles, I just stress putting in a relay to power them.

The relays aren't too difficult, I actually prefer them because you can hook them up to your ignition switch and when you turn the truck off the relay turns off, also with relays you don't burn out switches.

 

[82chevy350]

Anyone find a diagram on this?

 

[farmerchris]

some reading on this http://madelectrical.com/catalog/rly-1.shtml

 

[Green79Scottsdale]

I bought a pre-made harness from United Pacific to do mine. Simple to hook up.

 

[82chevy350]

id like to make my own rather than paying for one. Id really like to convert to a better fuse block where I can incorporate relays and such I may try to find one from a 96 chevy or something.