Why does my interior light stay on all the time?

The most common causes are a stuck door switch, a switch turned to the manual on position, or a misaligned door latch holding the switch open. Check all door switches before assuming a wiring fault.

Can I fit LED interior lights?

Yes, but on CAN bus vehicles you may need bulbs with built-in load resistors to prevent bulb-out warnings. Confirm the LED is the correct polarity, format, and current draw before fitting.

Will an interior light drain my battery overnight?

A 5W festoon bulb left on overnight will draw enough current to noticeably reduce battery state of charge, especially in winter. Two or three nights and a healthy battery may be flat to the point of failing to start the car.

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Interior Light buying guide — what to know before you buy

Interior cabin lights provide illumination for the driver, passengers, and rear cargo area. Most are factory-fitted with festoon or wedge incandescent bulbs and operated by door switches and a master control. Modern vehicles often use LED modules with CAN bus control for dimming and sequencing.

When to replace

Interior light failure is usually a simple bulb change, but persistent issues point to a wiring or switch fault that drains the battery.

Bulb does not light despite a working circuit
Light remains on with all doors closed — drains battery
Lens cracked or broken
LED module flickers or shows uneven illumination
Plastic housing damage from impact or repeated removal

What to look for when buying

Interior light formats vary widely. Confirm the bulb type and the housing fitment before ordering.

Bulb format — festoon (C5W, C10W), wedge (W5W, T10), or BA9s
LED upgrades — confirm CAN bus compatibility to avoid bulb-out warnings
Replacement housing must match the original mounting clip pattern
Some vehicles use a sealed LED module — bulbs are not separately replaceable
Check polarity if upgrading to LED — wedge LEDs are direction-sensitive

Common failure modes

Most interior lights fail through bulb burn-out or door-switch issues, but some patterns recur.

Bulb filament failure with age
Stuck door switch causing the light to stay on and drain the battery
Courtesy light switch contacts corroded from spilt drinks
LED module driver failure — entire unit goes dark
Cracked lens from forced removal during bulb change

Related parts to check together

A constantly-lit cabin light is a classic flat-battery cause. Inspect related switches and bulbs together.

Door switch — usually a small plunger that activates with door opening
Courtesy light switch — control panel position should toggle door, off, on
Cabin light bulb — confirm correct format before replacement
Battery — check state of health if the light has been left on for extended periods