In case anyone's looking for it, here's a good diagram that explains hooking up aux relays for headlights. For one beam pair, just use one of the green or black circuits and one relay.
The outer lights in this picture would be a 9005 style (dual high/low beam in one light). This picture shows the center pair of lights (also called high-beams but perhaps more properly called aux. high beams) coming on when the outer 9005 high-beams are activated.
For simplicity, you could just ignore the pink/black/red circuit and concentrate on the green/black/red circuit.
To relay one pair of headlights you would just:
1. Disconnect the existing wiring to the headlights you want to upgrade with a relay (only one relay is usually necessary per pair);
2. Attach pin 86 of the relay to your existing headlight "on" switch (whether that's the high or low beam wire - depending upon which lights you are adding relays to). The gauge of this wire doesn't matter since it will only be running the coil within the relay - in this diagram it's the green wire to "existing harness";
3. Attach pin 85 to a new ground wire to a good ground or the battery ground. The gauge of this wire doesn't matter since it will only be grounding the coil within the relay.
4. Attach pin 30 of the relay (in this diagram the red wire)to a beefy wire directly to the battery (and fused as close to the battery as possible). This will be the beefiest wire in the system because it will supply the current to both headlights;
5. Attach pin 87 of the relay to a beefy pair of wires (in this diagram the green wires going to the central pair) each running directly to the + connections on the head lights or auxiliary lights. These wires can be 1/2 as beefy as the ones in paragraph 4 because they will only carry half the current as the one in paragraph 4.
6. Attach the ground connections of the headlights to a pair of ground wires (as least as beefy if not beefier as the ones you selected in paragraph 5 above) to a good ground or the battery ground.
Done.
A note on "Beefiness" of wire gauge:
You can determine the gauge of wire to use based on your anticipated current draw using a table like this:
Code:
Length of run (in feet)
Current 0-4 4-7 7-10 10-13 13-16 16-19 19-22 22-28
0-20A 14 12 12 10 10 8 8 8
20-35A 12 10 8 8 6 6 6 4
35-50A 10 8 8 6 6 4 4 4
50-65A 8 8 6 4 4 4 4 2
65-85A 6 6 4 4 2 2 2 0
85-105A 6 6 4 2 2 2 2 0
105-125A 4 4 4 2 2 0 0 0
125-150A 2 2 2 2 0 0 0 00
Hopefully this helps someone.
