Headlight Repair and Installation Tips

February 23, 2012

Headlight installation is a simple procedure, but headlight repair requires some diagnostic finesse. Learn how to troubleshoot and repair headlights.

Headlight Installation

Even new vehicles will eventually require some form of headlight repair. Headlights may dim and need to be polished or cleaned, the bulbs may burn out, or they may even be broken in a minor accident. While mechanics can do every kind of headlight repair, they are many things you can do yourself for a fraction of the cost.

Lens Cleaning
All headlight lenses, even on the most expensive cars, can grow cloudy and need to be cleaned. Check the headlight lens--it may simply be cloudy or dirty on the outside, in which case it can be cleaned with a simple glass cleaner or plastic safe degreaser. For more serious clouding or scratches, care must be taken to not further damage the lens. Toothpaste, rubbing compounds, buffing and other abrasive techniques only work on glass headlight lens, but will further damage plastic lenses. Only completely liquid, non-abrasive cleaners made specifically for acrylic headlight lenses can be used to clean them. If there is condensation or clouding on the inside of the lens, it needs to be removed to be cleaned, and the seals around the headlight lens need to be replaced or fixed.

Bulb Replacement
When a headlight bulb blows, it's possible to replace it yourself on most cars. First, determine what kind of bulb you need. Check your owner's manual. If it isn't available, many auto parts stores have parts catalogs that will let you look up the year, make, and model to find the appropriate headlight bulb. Check out the car and the manual to determine how to replace the bulb. Many cars have a panel that allows you to insert the bulb from behind the headlight, and most manuals show the proper way to install the bulb. Make sure not to handle the bulb too much. The oil from your fingertips can damage both the glass and metal, causing the bulb to blow out much sooner.

Minor Repairs
The final common repair even amateur car owners can perform is a temporary fix for broken headlights or taillights. Whether they've broken in a minor accident or from backing into an unseen pole or shopping cart, it's important to immediately seal them so the light bulb and the light socket aren't damaged by moisture. For headlights, clear plastic and tape works, but tail lights require red tinted tape and plastic. Auto part stores offer both clear and red tinted headlight tape designed to seal out moisture. For a small crack tape is enough, but for a mostly missing headlight a sheet of appropriately colored flexible plastic, also available at an auto parts store, may be required. While taping the light up will avoid immediate moisture damage, these tapes are not meant to be used permanently, and having the head or taillight replaced will be necessary.

How to Install a Headlight Harness

Installing a headlight harness is not difficult. The most important aspect is whether to use a pre-made kit for a specific car or create a brand new harness out of a few pieces of wire along with a few male and female connectors.

Determine Harness and Headlight Type
The most important step is determining what manner of headlights will be harnessed to the vehicle. Some vehicles require a higher investment in time and labor compared to others. The simplest method for installing any wiring harness for a given vehicle is to use a pre-made kit.

These kits come with detailed instructions on exactly what to do. However, creating and installing your own harness is usually a cheaper and more customized job for the experienced individual. The items required for this are 16 to 18-gauge wire, some male female connectors and two relays.

Check the Harness Length
Make certain the vehicle's engine is cool then lay out the wiring harness on the engine bay to determine whether or not it is long enough for the task. Extra wire may need to be added or a new harness may need to be acquired depending on the preference of the vehicle owner.

Connect the Power Lines
Temporarily remove the fusible links from the rest of the harness to make this step easier. Once these are removed, attach the red power wires of the "O" terminal to the positive terminal of the battery. Then attach the black ground wires to factory ground set, or a heavy metal portion of the vehicle. If a custom harness was crafted then it is important to have wires designated and marked as power and ground before this step.

Attach the Socket and Ground
Plug the new socket into the bulb then attach the ground wire to a major metal section of the vehicle. Be certain that the portion it is attached to uses a solid screw and is of a material type that will remain corrosion free. There are many issues that can crop up due to improper grounding. If at all possible, connect the ground wire to the negative terminal on the battery.

Perform the same steps on the other headlight once this is completed.

Plug in the Relays
Plug in the relays and cover with electrical grease to prevent corrosion. Be certain the connection is secure and check over the entire harness to be certain everything is attached properly. If you disconnected the power wires earlier to make it easier to attach them to the positive terminal, make certain they are properly attached before continuing to the final step.

Check Light Quality and Clean Up
Turn on the lights and check to see that they are working properly. If they work on all settings and have no noticeable issues then the job is complete. If not, turn them off and go over the steps again.

One final item of note: If a vehicle has more than one battery then it may be necessary to hook the lights up to both of them.