Exterior Daylight Sensor?

I don't think the US models have a light sensor. There is a small lens on the passenger side of the dash near the window, which according to the owners manual is for auto headlights (not offered in the US), so I suspect there's nothing under the lens.

You can adjust the interior light intensity using the thumb wheel to the left of the steering wheel (next to the exterior mirrors control), and if you roll it all the way up past the click, it will not dim the interior lighting when you turn on the headlights.

 

The sensor is under there, andit's possible to set up auto lights. i did it!

 

Just like Flaninacupboard has already done, I plan to have mine "wired" up to the existing sensor (lens circular button looking thingamajiggy) to enable auto-headlights thanks to this awesome thread ! It's one of those cool evolution/discovery threads so you may want to read it from the present to the past.

 

It's a good mod!
If my company didn't take such a dim view of it's employees modifying fleet vehicles, I would have done this before I burned the first tank of gas in "my" G3.

Why in the world the folks in Aichi didn't include this feature in the US models---especially since the photocell is already installed, is a mystery to me!!! !!!!

 

I suggest you try covering the photocell looking circular button we discussed on this thread and see if that keeps your illumination from adjusting. If so, you have your answer.

I read on one of these threads of a guy/gal that drove in a tunnel with headlights on and notice the illumination adjusting and was thinking it was the photocell that we are talking about. Good luck with your findings.

 

Originally it was because the U.S. models had HID headlamps, and there was a concern about cycling. Now that HIDs are gone, I'm not sure why we don't get auto headlamps.

Tom

 

I assume you've also tested to see if the dimmer switch was in the fully up position, past the click, or not?

The shifter is lit from the overhead console (not internally lit)--have you looked for the light source overhead?

 

How long did you wait after you unblocked the sensor? I did the auto headlights mod and when I was testing it after I got it working it threw me off a little because there's a bit of a delay when the light input changes. If the headlights are off, but on auto (after the mod) and you block the sensor it takes about 30 seconds before the lights go on. Likewise, if the lights are on and you unblock the sensor it takes about 30 seconds before they turn off.

This design makes sense if you think about it... you don't want your headlights coming on for a few seconds every time you drive under a bridge in the day, or turning off for a few seconds every time you drive under a street light at night. So the car waits for a little while to make sure that the light level really has changed before it activates or deactivates the headlights.

I'm thinking that you might be seeing the same effect and you may need to wait 30 seconds or so after covering or uncovering the sensor to see any change.

 

OK, that means it works with the dash board lighting. When you turn on parking lights, it also lights up.

 

I didn't realize the Prius had that--a few of my previous cars had a sensor on the dash that sensed the sunlight direction, to adjust the A/C in appropriate sections of the car.

The owner's manual says this about the sensor on the dash:

Headlight control sensor (if equipped)
The sensor may not function properly if
an object is placed on the sensor, or anything
that blocks the sensor is affixed to
the windshield.
Doing so interferes with the sensor
detecting the level of ambient light and
may cause the automatic headlight control
system to malfunction.