6th Oct 2017, 09:07

Lights whose switches have an "AUTO" mode DO have a light sensor. Modern cars whose headlamps are always on (especially North America) will have their Daytime Running Lamps (DRLs) on. When the ignition is turned on, the headlamps (in these cars) turn on to low beam. Some cars, instead of headlamps, have other means of complying with DRLs - some have LED strips, some have bulbs that light up either within the headlamp cluster (but not the low beams) or the foglamp assembly. Operational difference between DRL and AUTO mode - many cars with DRLs do not turn on tail lamps (or other related lights) when activated, the sole purpose of the DRL is to make sure the car is visible from approaching vehicles, especially in 2-way roads. The AUTO mode, sensing it is actually dark (not just night, when you drive through a tunnel for example), and turns on the main lighting system - low beams, tail and side (parking in the US) lamps, and instrument cluster lamps in lieu of the driver turning the lighting switch to the second click stop. There are also cars which WILL turn on tail lamps with the DRL. One difference also - in DRL, if the low beam headlamps are used for such, you cannot change from low to high beam (even if you can flash them normally); in AUTO mode, functioning as if the light switch has been turned to the second click, you can operate the dipswitch/dimmer to change between low and high beams.