Credit goes to :SlitheringJoe at Jeepforum.com

It is simple to build your own Headlamp Relay Harness. Below is specifc to a TJ but can be applied to just about any car that utilizes only a switch to control the headlamps. A relay harness constructed with short length heavy gauge wiring will enable one to get the most light output from their current headlamps whether they are sealed beam, H4 conversions or higher wattage bulbs.
You will not have to cut any factory wires. You will use one of the existing headlamp connectors to trigger the relays. The other headlamp connector will be taped up and shoved away. Many automotive parts stores carry replacement headlamp connectors. Get the ones that will work for you application.

Headlamp Relay Harness Schematic:



The itemized parts below can be found at www.rallylights.com


(2) Hella Waterproof/Weatherproof Skirted Relays (**):
(Item #HL87411, SPDT, Resistor)



(2) Hella Waterproof/Weatherproof Relay Base(**):
(Item #HL87173, 5-Wire)


(**) To lower the cost, you can use standard Hella relays. All Hella relays are designed to be used in an underhood automotive envirionment but it is recommended that waterproof/weatherproof relays are to be used if they are excessively exposed to mud and water.

Below are available at any Pep Boys, Autozone, Advance Auto, or a similar auto parts store)

(2) Mini-Fuse Relay Holders, 12GA:


12GA Wiring
16GA Wiring
(3) Male Quick Disconnect terminals (16-18GA, 0.25-inch)
(2) 20A Mini-Fuses
(2) H4 Headlamp Replacement Connectors (Female) (HL28001 H4 Replacement Female Socket, 10 gauge)

(note: I have been trying to find all these parts at one site and havent been able to as of yet...rallylights.com is out of the HL28001 (discontinued))