Adding automatic headlights to 2012 Prius V

Depends what you mean by auto headlights. If you mean lights that turn on and off with the car, it has them and a timer option. You just leave them on and the auto function works.

If you mean auto dimming, the answer is no.

 

What you're asking about was standard on the 2012 v Five. No idea on other trims.

 

Standard on every trim I believe, certainly on a v3. The switch does not have to say "auto". You turn the lights on when in Ready and leave them on when shutting off. There is configurable off time setting in the head unit. Default is 30 seconds.



My headlight switch has been on for years. I changed the default 30 sec to zero since I don't need to light the driveway as I enter the house. Realize this basic feature runs the lights during the day when in Ready. I and my insurance consider it is a safety feature since the car does not have DRL, daylight running lights.

 

That's a description of auto off. It's in every trim. You just leave the switch ON, and the lights get turned off when you leave the car.

If you're looking for auto headlights, where you use the AUTO position and the light sensor turns them on when it's dark and off when it's light, that wasn't in every trim. You can follow this thread for how to add it.

It's a nice feature because the light sensor also controls the instrument brightness, independently of the headlights. So you can drive in those dawn or twilight hours and the headlights will be on but the instruments won't be too dark to read.

Automatic dimming, where the car selects low or high beams for you, well, that would be a third different thing.

 

There is a light sensor for the instruments standard.

 

The single light sensor on the Gen 3 dash is always used by the HVAC (to adjust for driving through sun and shade), and it is used for the auto headlights and instrument dimming in some trims.

In some trims without, the wire from that sensor back to the body ECU is missing, so it cannot control the headlights or the instrument brightness. The details are covered in this thread also linked in #7.

In my 2010 liftback, sensor control of the instrument brightness didn't start happening until I completed that wire run from the sensor to the ECU. Then I immediately got automatic instrument brightness, which is worth the price of admission even if you don't go on and finish the auto headlights.

To get the auto headlights, I then had to add one more wire that grounds L7 pin 28 when "auto" is wanted. I bought a stalk variant with the AUTO position and ran the wire to L47 pin 19 where the stalk plugs in. The rest of the details are in the linked thread.