Automotive Lighting FAQ

Proper lighting can mean the difference between a safe drive home at night and an unfortunate incident. Here are some tips and information about getting the most out of your car's lighting.

Q: What do the codes like H4, H7, HB4, P21W, etc, mean?

These are universal short codes indicating the bulb type and dimensions. Different vehicles use different bulb types depending on the original lamp design.

Q: What is meant by color temperature?

The Kelvin (K) is the unit of color temperature. The 3900K to 4300K range is the brightest, most natural white light similar to that of daytime sunlight, and therefore the color temperature most recommended. It is also the typical color temp used by car manufacturers. Higher color temps like 6000K have a blue-ish light, which is more fatiguing to the eyes, both to oncoming traffic and to the driver. Oncoming cars will see your lights for only a brief time, but as the driver, you must deal with it for the duration of your drive. The bluer the tint cast on the road and surrounding area, the more quickly your eyes become tired. 2500K lights have a yellow color, which is more suited for bad weather conditions like rain, fog or snow.

Q: Why can't I touch the bulb glass with my fingers? What happens if I do?

When your fingers come into contact with the bulb glass, alkaline compounds and oil residue are transferred onto the glass. When the bulb is in operation, these cause uneven heating at the contact spots, which can weaken the glass structure. As a result, bulb lifespan will be reduced, the glass may crack under uneven heat conditions, and in rare extreme cases, the bulb may even explode. Therefore, always use gloves when handling bulbs, avoid touching the glass with bare hands.

Q: What is the difference between halogen, LED, and xenon lights?

Halogen bulbs are the "standard" light bulbs typically used in most regular vehicles. Halogen bulbs are filled with a halogen gas (usually iodine), and a filament inside made of tungsten is heated by an electric current, which causes light to be emitted. Halogen bulbs are less expensive compared to xenon and LED light, only have a life span of about 250 to 400 hours. As a result, they need to be replaced more often.

LED lights have replaced xenon light bulbs as the standard for luxury class and upper mid-range vehicles, and is becoming more popular even in lower-priced cars. The trend is clearly moving in the direction of LED light: it is likely that it will completely replace xenon and halogen lamps in the not too distant future. They are brighter than halogen lamps, use less energy, and are far more durable - lasting to up to 15 years. It is also possible to finely control the output, which allows the luminous intensity and the direction of the light cone to be optimally adjusted to the relevant traffic, weather and visibility conditions. Unlike xenon lights, LEDs normally do not require a projector housing.

Xenon headlamps, also known as High Intensity Discharge (HID) lamps, have a special xenon gas discharge lamp in the low beam or in the high beam. This means that the lamp is ignited under high voltage (20,000 volts), creating an arc. This means that xenon headlamps are many times more light-intensive than halogen lights or LEDs. They are also energy efficient, though not as much as LEDS, and have a longer lifespan than halogens, but not as long as LEDs. They are also very expensive. Xenon lights typically require a projector housing to focus the light beam, otherwise the lighting can be scattered and blind oncoming traffic.

Q: Do I need any upgraded wiring to upgrade bulbs?

For Bosch and PIAA bulbs, it is not necessary. These bulbs draw factory wattage and will not harm any of your wiring. For other brands, check the technical specifications or instruction manuals that come with their product.

Q: Do I have to change the left and right bulbs at the same time?

We strongly recommended to replace bulbs as a pair, especially for headlamp and fog lamp applications. After a period of usage, bulbs will start to dim. Replacing only one bulb will lead to light imbalance. That’s why Bosch and PIAA bulbs usually come in a set of 2.

Q: My bulbs keep failing; why does this keep happening?

Bulb failures caused by voltage surges have become more common as new vehicles have placed greater demands on factory electrical systems. The main lamp ground wire must be connected to the battery negative terminal or to a cable leading to it. If a voltage surge occurs, the bulb will look like it was struck by lightning! The metal base and glass will be burnt or the filament will blow up!

Check all connections. A loose connection can cause pre mature bulb failure. There are often power spikes on vehicle start up. Make sure your lights are off when starting your vehicle. You can test for these spikes by using a voltage tester at the light harness where it plugs into the lamp. Anything over 13.6 volts would be considered a spike.

Other causes for short bulb life or blown fuses:

- Check the wiring leading to the lamp. Look for wiring that has been cut, burnt, or worn through. Tape over or replace wiring.

- Check the plug-in connectors from the lamps to the wiring harness. If the connections are corroded, clean them, then fill the connectors with a dielectric (non-conductive) grease or electric terminal dressing to keep moisture out.

- Check inside the lamp. Make sure the rubber insulator over the positive white wire is completely covering the connection between it and the bulb pigtail (it "snaps" into place when fully seated).

Q: What is the difference between a fog light & a driving light?

Fog lights provide illumination forward of the vehicle that enhances visibility in fog, rain, snow, or dust. Fog lights are intended to be used in conjunction with standard headlamp low beams. Driving lights are mounted to provide illumination forward of the vehicle and intended to supplement the high beam of a standard headlamp system. It is not intended for use alone or with the low beam of a standard headlamp system.

Q: My auxiliary lamps have water in them, how can I stop this from happening?

Some moisture inside the lamp is normal, especially in damp conditions. The lamp should dry out after a few minutes of operation. If it doesn't, check the following:

- The lens may be upside down. The PIAA name must read right side up so the vent on the bottom can drain.

The lens/reflector unit may not be mounted tight against the lamp housing. Loosen, then re-tighten the screws.

- The gasket may be twisted or pinched. Some gaskets have a vent gap.Make sure it's on the bottom.

- Lamps with a "Snorkel" type wiring grommet in the back of the housing must have the opening facing down.

- The PIAA name on the lens must be right side up or the vent will be on the top and fill the lamp with water. Make sure the lens vent is clear and any other vents, such as the "snorkel" grommets on the back of some lamps, face down. The gasket must be straight and the lens fitted firmly to the housing.

- 90 Pro lamps have a vent on the back of the housing. If the lens is turned over, the vent must be reversed also.

Q: Can I mount my auxiliary lamps upside down?

PIAA lamps are designed to function properly mounted upright or upside down, as long as a few details are taken into consideration. When mounting your PIAA lamps opposite of their intended installation, remember that lamps with a "Snorkel" type wiring grommet in the back of the housing must have the opening facing down. Also, the PIAA name must read right side up so the vent on the bottom can drain. Proper auxiliary lamp aiming is the most important part of an installation. Refer to the Light Aiming Instructions on this web site for proper alignment.

Q: Are auxiliary lights these legal?

Lighting laws vary from country to country and state to state. It is the responsibility of the user to ensure that he obeys all applicable local and federal laws. PIAA lamps are intended for use solely as auxiliary lighting. Auxiliary lamps are designed to improve visibility during night time motoring and inclement weather conditions. However, irresponsible use of any auxiliary light can be dangerous and illegal.