Main light switch
Identifies the switch that turns the exterior lights on — on many cars a rotary knob or the end of the left stalk.
What pressing it does
Turning it selects the lights. Hyundai's Tucson knob, at the end of the left stalk, has OFF, AUTO (lights on and off by an ambient-light sensor), position lights (with the number-plate and instrument lights) and headlights.
Check your car's manual: makes and models differ in what a button does, which positions a switch has and whether it works with the engine off, and your owner's manual is the authority for your car.
- What it looks like
- A lamp drawn as a circle with rays around it
- Also labelled
- Master lighting switch; Lights; Headlight switch
- Standard
- UN R121 and FMVSS 101
What to check in your car's manual
Which positions your switch has, and what AUTO does on your car.
Where makes differ
Hyundai notes that even with AUTO on, it recommends switching the headlights on by hand at night, in fog or rain and in tunnels and car parks. FMVSS 101 allows the word 'Lights' instead of the symbol.
Where the regulations list it
| Rule | Row | Function | Must be lit with the headlamps |
|---|---|---|---|
| UN R121 | Table, item 1 “Master lighting switch” | Control | No |
| FMVSS 101 | Table 2, “Master Lighting Switch”: symbol or the word “Lights” | Control | — |
UN Regulation No. 121 (01 series), location and identification of hand controls, tell-tales and indicators: Cars (M) and light goods vehicles (N1) approved under the UN 1958 Agreement, which includes the EU, UK and Japan. Paragraph 5.2.1: where fitted, a control listed in the table is identified by the symbol in its column 2; note 2 says the symbols are substantially identical to those of ISO 2575:2004. US Federal Motor Vehicle Safety Standard No. 101, Controls and displays (49 CFR 571.101): Cars, multipurpose passenger vehicles, trucks and buses sold in the US. S5.2.1: a control listed in Table 1 or Table 2 is identified by the symbol in column 2 or the word or abbreviation in column 3. S5.3.1(a): a control marked 'Yes' for illumination must have its identification lit whenever the headlamps are on, except on the floor, console, steering wheel, steering column or windshield header.
Good to know
- UN R121 note 12: its tell-tale is not required if the instrument lights come on automatically with the switch.
Related dashboard pages
Other buttons under “Lamps”
Sources
The symbol is cited to the regulation rows above; what pressing it does is taken from the owner's manual below. Each document was read on the date shown.
- UN R121: UN Regulation No. 121 (01 series) as published in the Official Journal of the EU, L 5, 8 January 2016, pp. 16-19: table 'Symbols, their illumination and colours' checked 2026-09-25
- FMVSS 101: govinfo: 49 CFR 571.101 in the Code of Federal Regulations, 1 October 2025 edition, Table 1 (pp. 329-332) and Table 2 (p. 334) as printed checked 2026-09-25
- Hyundai 2025 Tucson (general market, English web manual): Lighting control — OFF, AUTO, position light and headlight positions; AUTO uses an ambient-light sensor; manual use recommended at night, in fog, rain and tunnels. checked 2026-09-25
Written in our own words; the manuals cover their own models only.