swapping 1990 grill with 2 side by side headlights to 1985 with 2 stacked headlight per side. Lots of questions?

[1990Jimmy]

I don't like the 1990 GMC Jimmy factory grill with 2 per side, side by side headlights set up. So I swapped the core support to a 1984 one with 2 per side stacked lights. Also bought 4 new glass headlight housings that take H4 bulbs. Now how do I wire this stuff? I'd like to do 2 light on in low mode and 4 lights on in high mode? Any advice on H4 bulbs and wiring would be great.

 

[Big Ray]

As far as keeping the low beams on, there's a simple relay mod that will do that. Did it on my 89 pickup. Summit sells a kit or you can diy if can wire it up. Schematics all over the web.
Works great for power windows too. Need 2 per window, one for up, one for down.
Iirc, the H4 was remove and replace. Put them in my bikes when I was still riding.

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Website i stole the schematic from...

Headlight Improvements - '60 - 66 Chevy/GMC Trucks

It says 60-66. It works on our trucks. This wiring puts more light out as well. Full power from the battery, instead of dropping voltage from too small of wire, corrosion from the age of our trucks, and now it doesn't go through the headlight switch. The headlight switch simply activates the relays, they handle the heavy current.

 

[Raider L]

@Big Ray,
Yeah, I didn't think about a relay. When I was rebuilding my '74 I wanted to do the same thing to confuse people as to what year truck they were looking at, ha, ha, but for the more obvious reason to have more light hit the road. Just think, when I first bought the truck in '81 it had sealed beam head lights still in it. Then someone said to get the Halogen headlights and it made a huge difference in light on the road.
But I was looking at swapping out the radiator support and didn't know if it would fit or not. But I was thinking that if you want to do the wiring there is a wire in the plug that lights the low beam filament, and a wire for the high filament that comes from the bright switch on the floor, and a ground wire. All in the plug in the back of the headlight. Just tap into the low beam wire and the same for the high beam wire and take it down to the plug in the other light. Wouldn't that work? What happens if you don't use a relay?

 

[Big Ray]

I like the relay because it routes full current away from the headlight switch and the old, restrictive wiring on our trucks.
The headlight switch becomes just a "switch" to activate the relay.
As far as connecting the hi/lo wires, halogens draw a lot of current. You're asking for trouble imho.
I put a halogen in my bike, it melted the stock headlight plug.
Your mileage may vary, of course.

 

[gmbellew]

I like the relay because it routes full current away from the headlight switch and the old, restrictive wiring on our trucks.
The headlight switch becomes just a "switch" to activate the relay.
As far as connecting the hi/lo wires, halogens draw a lot of current. You're asking for trouble imho.
I put a halogen in my bike, it melted the stock headlight plug.
Your mileage may vary, of course.

to fire the lows with the highs, you need another set of relays to trigger the lows using the highs as the "switch" without adding extra amps to any of the wiring.