Recent I bought a high-mileage 2004 Dodge Ram 1500 pickup truck. Even though I bought it mostly for its utility, hauling yard waste and such, I still wanted it to look nice. Overall it was in good shape but the headlights were noticeably glazed and a bit yellow. After an unsuccessful attempt to revive them using an over-the-counter "headlight lens reviver" I decided to just replace them. And to add a little "bling" I decided to upgrade to halo (sometimes called "angel eyes") headlights.
To replace the headlights in a similar vehicle you'll need:
- Replacement headlights that match your vehicle model
- 16 or 18 gauge electrical wire
- Quick splice wire connectors
- Electrical tape
- Wire ties
- Hand tools (screwdriver, pliers, Torx bits, depending on vehicle)
NOTE: This Instructable deals with "jacking in" to your vehicle's electrical system. Serious damage can occur if you mess up the connections and create a short. If possible you should disconnect your negative battery cable whenever working on the electrical wiring in your car.
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Step 1: Get Yourself Some Awesome Headlights
Obviously one of the first things you need to do is find yourself some awesome headlights. One of the great things about the Internet is the number of options available. A few things you should consider is whether you want direct "factory replacement" headlights or something more glitzy. At the high end are High Intensity Discharge (HID) headlights--the ones that make your car look like a spaceship from Close Encounters. I decided against these for a couple reasons. The first was cost--I just couldn't justify spending the multiple hundreds of dollars for headlights on a used pickup. Plus you typically need extra hardware to handle to high current requirements of HID lights if your vehicle wasn't designed for them. LED-based halo headlights aren't as bright but don't require extra hardware and are pretty common from sites like Xtralights.com--just enter your vehicle info and get a list of compatible lights. I decided to go with a set from Spyder that featured not only the halos but some accent LEDs as well.
Step 2: Sort Out the Wiring
The headlights I ordered came with halogen high- and low-beam lights already installed and wired to a standard automotive headlight connector. Good news! That would be the easy part. The LED halo and accent lights were terminated with plain ol' wire--no connectors in sight. Assuming your lights are similar the first thing to do is sort out the various lighting components and the positive/negative polarity of the circuits since LEDs, unlike incandescent bulbs, must be wired correctly. In my case the accent LEDs had red/black wires and the halo LEDs had white/black wires. Black would be negative in both cases so that made the next step pretty simple.
Step 3: Splice the Common Wires
Determining when the headlights go on is pretty simple since you'll just be using the standard connector linked to your vehicle's headlight switch. For the LED parts the choice is really up to you. You can link them to the headlights or, like me, have them come on whenever the vehicle is running. Since I wanted both the halos and the accent lights to come on together I first spliced all the common wires together on each headlight assembly. that means all the positive wires (red and white) together and all the negative wires (black) together. I spliced each bundle to a piece of new wire about 5 inches long that I'd use later to connect to the truck's wiring.
Gizmologist has an excellent wire splicing Instructable but since this was for a beat up pickup truck and not the Space Shuttle I opted for a quick and dirty splice. However, I did solder the connections and cover them with heat shrink tubing (partly because heat shrink tubing is just cool to use).
Step 4: Splice the LED Negative Wires to the Headlight Negative Wire
Since the negative (ground) circuit is common to all the circuits in the vehicle, I decided to splice the newly soldered negative wire bundle from the LEDs to one of the negative (black) wires of the halogen headlights. This would keep the wiring more compact and simpler if I had to remove the new headlights down the road.
I used a "quick splice" connector available at any auto parts store to connect the soldered wire from the LED black wires to one of the black wires from the halogen headlights.
NOTE: if you don't use waterproof connectors (I didn't) wrap the splices with electrical tape to give them some protection from the elements.
Step 5: Remove the Factory Headlights
Now that the new headlights are prepped it's time to get those old, nasty ones out. On my Dodge this was pretty straightforward. They are held in by just three Torx-head screws. Opening the hood exposes two screws on the side of the headlight assembly. The third screw is hidden underneath the assembly and is a bit trick to get to. I found it helpful to remove the two screws holding the plastic bumper cover to the inside of the fender and carefully prying back the cover so I could get a long screwdriver extension into the gap. Once the screws are removed the headlight assembly pops out with just a little effort.
With the assembly pried free, you'll need to disconnect the headlight connectors and, in my case, the turn signal fixture as well. My replacement assembly reused the turn signal so be careful not to break it! It is removed easily with a quarter turn of the housing. The headlights have a plastic ring that holds them in place and it also is loosened with a quarter turn.
Once the headlight is removed from the assembly, remove the halogen bulb from the connector by prying up the plastic tab and carefully pulling the bulb out of the socket.
Step 6: Run Wire for the LED Lights
Since I wanted the LED lights to come on whenever the vehicle was running I needed to find the accessory circuit (also known as the cigar/cigarette lighter circuit) since this circuit is only live when the key is in the ACC position. The simplest way was to "piggyback" on the accessory fuse which, thankfully, was located in the engine compartment and the location was listed on the underside of the fuse box cover. If your fuse box is the passenger compartment you may need to run some wires through the firewall. (Alternatively I did find a Dodge Ram maintenance manual online that identified the accessory circuit in the wiring bundle but I didn't feel like jacking into the trucks "nervous system" just yet.) I looped some general purpose automotive wire around the base of the fuse and strung it along the body and into the two headlight cavities and secured it with wire ties.
NOTE: It is important that you loop the wire around the fuse post that is "downstream" from the fuse itself. This ensures that, in the event of an overload, the LEDs are disabled when the fuse blows. I used a voltmeter with the key turned to ACC to determine which side carrier current. In my case it was the side closer to the radiator but this may vary with your car.
Step 7: Splice in the LED Lights (and Connect the Halogen Headlights)
The LEDs (like all lights) need to be connected both a positive and negative (ground) circuit in order to work. The negative side was addressed earlier by splicing the black wire bundle into one of the negative wires from the halogen headlights. The wire running from the ACC fuse provides the positive side and the next step is to splice the red/white wire bundles soldered together earlier to the wire run from the ACC fuse.
Once the positive bundle is spliced in you can connect the halogen headlights using the factor connector (no photo but it should be pretty obvious) and reinsert the turn signal into the provided socket.
Step 8: Reconnect and Test
If you disconnected the negative battery cable go ahead and reconnect it and watch for any sparks and/or smoking...that would be bad. Disconnect the battery cable and check your wiring.
If you've done everything correctly (headlights reconnected, black wires to common ground, red/white wires to ACC circuit) then the LEDs should light when you turn the key to ACC and headlights should come on when you turn the headlight switch.