Halogen festoon bulbs – C5W and C10W festoon

The festoon bulb (or festoon) is a cylindrical bulb with a metal contact at each end, held by pressure between two clips in its holder. It is mainly used for the vehicle’s interior lighting: dome light, reading light, trunk light, glove box and license plate light. The two common references are the C5W (5 watts) and the C10W (10 watts). Festoons come in several standardized lengths: 31 mm, 36 mm, 39 mm and 42 mm, to be adapted depending on the vehicle.

The length of the festoon bulb is the essential criterion for choosing the right bulb. Remove the original bulb by releasing it from the retaining clips, then measure it from one metal end to the other with a ruler or a caliper. Standard sizes are 31mm (compact, glove box), 36mm (the most common, dome light and trunk), 39mm and 42mm (license plate lighting). A festoon that is too short will not make contact, one that is too long will not fit into the holder. AGM Vision product sheets indicate the exact length in millimeters.

The C5W and the C10W are both festoon bulbs, but differ in their power: 5 watts for the C5W and 10 watts for the C10W. The C5W is the most common and is fitted to most dome lights, trunks and license plate lights. The C10W provides brighter lighting and is found on certain vehicles requiring higher brightness. Both can exist in the same lengths, but do not draw the same current. Always install the original wattage to avoid overheating the plastic holder or an error on the dashboard.

Replacing a festoon dome light bulb is very simple. Gently pry with a flathead screwdriver or a plastic tool to remove the dome light cover. The festoon bulb is held between two metal clips by pressure. Release it by pushing it to one side, then pulling it out. Insert the new festoon by positioning it between the clips and pressing lightly so that it clips into place. The operation takes less than 2 minutes. Same procedure for the trunk and the glove box.

No, beyond the length which varies from 31 to 42 mm, the diameter of the festoon bulb also differs depending on the references. Standard C5W and C10W festoon bulbs have a diameter of about 10 to 11 mm. Some high-power versions or replacement LEDs may be slightly wider. If the housing is narrow, a bulb that is too wide will not fit. Check the full dimensions (length and diameter) on the AGM Vision technical sheet before ordering. The dimensions of the original bulb, engraved on its body, can also serve as a reference.

Yes, the French Highway Code requires a white license plate light. Standard C5W and C10W halogen festoon bulbs naturally produce a warm white light, compliant with this requirement. Any colored bulb (blue, red, green) is strictly prohibited for license plate lighting and results in a failure at the technical inspection. The power must be sufficient so that the plate is readable at 20 meters, at night. The standard halogen festoon bulbs sold by AGM Vision are all compliant with license plate lighting standards.