I upgraded my 01 F250 to 04-style headlights because my original aerodynamic headlights were foggy and sandblasted. I bought the replacement lights off ebay, and they worked great. Plug & Play.

I think Ford used too small a wire for the headlight circuits, and wanted to add relays and bigger wire. My truck has factory DRL's, and I wanted the option to keep them.

The kits I have seen use one relay for low beams and one for high beams, which means that if one side shorts out you lose both headlights. The factory system uses a separate 10 amp. fuse for each low beam to provide redundancy. I chose to use three relays in order to keep that same redundancy. The relays are: 1) High beam, 2) Left Low beam, and 3) Right Low beam.

Power comes from battery side of the starter solenoid. I ran wires from there to a fuse block just ahead on the fender inner panel by the right battery. I used a 4-fuse block (NAPA NW 720224) which uses mini ATM fuses. I did this so the fuses would be the same as the regular ones elsewhere on the truck. I ran a 14 ga. wire from one 15A fuse back to the cab for an accessory circuit controlled by a relay hot in RUN and ACC. A 15A fuse supplies the high beam circuit. Two 10A fuses supply the low beam circuits. These power wires go to the #87 post of each relay.

The high beam circuit is wired with 12 ga. wire. The low beam circuits are wired with 14 ga. wire. I have not measured the voltage at the lights, but they are so white that I can't believe that I have any voltage drop.

I used Bosch-style relays, SPDT. These are like the square ones Ford uses in most applicatons. I bought a pair of high-temperature headlight harness extensions for the 9007 bulbs off ebay in order to avoid cutting the factory harness. I cut the each low beam wire and ran the supply side back to the #87a post on the respective relay. I ran the light end of the low beam wire to the #30 post of the relay. This give me the DRL circuit when the low beams are not in use.

To trigger the low beams through the relay, I ran a wire tapped into the RD/YE wire at the DRL relay behind the glove box. Be careful to use the one that comes from the multifunction switch. There is also a RD/YE wire that comes directly from the main light switch to the DRL relay. You can tap in anywhere between the multifunction switch and the DRL relay. I chose that location because it was easy to find. I used one of the customer access wires to pass through the firewall and ran a 1/4" loom over the top of the engine tied to the large harness suspended below the vent grill. I also used this loom to carry my accessory circuit back to the cab. This trigger wire connects to the #85 post on each low beam relay. The #86 post of all the relays is connected to the factory ground screw near the starter solenoid. I also grounded the right headlight via the extension harness to that screw. I grounded the left headlight extension harness to the factory ground screw near that light.

I cut the high beam wire of the extension harness and connected the supply end with 14 ga. wire to the #85 post of the high beam relay. I ran the 12 ga. wire from the #30 post of the high beam relay to the light end of the high beam extension harness.

When the main light switch is off, the DRL powers the lights through it's regular circuit, passing through the normally closed (#87a) post of the relay. When the main light switch is on, the low beam circuit triggers the two relays to supply power through the normally open post (#87) of each relay. When the lights are on high beam, the factory system cuts the power to the low beam trigger and sends power to the high beam circuit, which triggers the high beam relay.

I can finally see at night!!!

 

I like posts like this - good work. Does anyone know if the 09 DRL low beams are reduced voltage? When DRLs were typically high beams, the voltage was reduced to extend filament life. I've been considering switching mine over to high beam DRLs.