High beam wouldn't hold sometimes. Defect?

It isn't as perfect as a driver - but generally quite good. It doesn't work well in a bright area, and more often than not, most mis-adventures it's played with have been from reflections from road signs. It also doesn't work well in the rain (and presumably fog).

Is the windscreen clean? I could be wrong, but I think it is tied in with the Forward Recognition Camera/sensor behind the rear vision mirror. It may work in conjunction with the Automatic Light Control sensor on the dashboard in the middle just behind the windscreen. Dust on the dashboard?

I believe in USA you can adjust the sensitivity (not in Australia). Instructions in the Owner's Manual.

 

You have to have the stalk away from you, AND the buttons near your knee like this - except your print won't be reversed:

 

It won’t go to high if it is not dark enough outside. I’ve had it dark enough so the lights come on but not dark enough to work the auto high beams. They did work as it got completely dark

 

Hopefully.

The automatic mode is not perfect. It is designed to dim not only for oncoming cars but also when you get close to a car ahead.

Because of that, I assume, it also dims sometimes because of street lights and other bright objects in it's "field of view".
When you activate it, the high beams will not come on if the system thinks they should be dim.

The point about being dark enough to activate the headlights at all is a good one too.
Of course, that assumes that the headlights are automatic. Odd situation with my C: It has automatic high beams but NOT automatic headlights. Pretty stupid design.

I have found it pretty much useless in town......but you probably shouldn't be trying to use high beams in town anyway.

 

If your headlights were halogen I'd say check both bulbs but because they are LED, check fuses, headlamp connections, switch stalk, wiring etc.
What I would do is turn Auto on, push the stalk forwards then find a really dark road and see if they work, on auto, under the correct conditions. If yes then you can eliminate all of the above and the fault most likely lies with the Auto button not turning off properly.

 

Yes.

If the headlight switch is set to 'off' or 'DRL' then the high beam lock (push stalk to forward detent away from driver) will have no effect.

You may have been looking at your DRLs, mistakenly thinking the low beams were on. The momentary beam flasher (pull stalk towards driver) is not inhibited by any other control on the car, so that doesn't care which state the switch is set to.

 

I can only speculate that they are trying to combine multiple functions into few controls with the aim of harmonizing it for multiple markets with diverging regulations.

The DRLs are usually interlocked to the parking brake, so engaging the brake would douse the DRLs with the stalk switch on. In this configuration, the car would pass the tests for municipalities where a car parked temporarily must have its parking, tail, lp & side markers on AND headlights entirely extinguished. Disengage the brake to drive and now it's in a configuration that will pass US & Canada lighting laws. One more click on the lighting switch cap and you get full headlights legal for everywhere they sell it.

Other cars are set up so that the parking lights are given their own switch, and sometimes with no driver control of the DRLs apart from the brake handle or something buried in a dashboard UI menu.

I can't say I've developed a full-fledged mnemonic device for remembering the lights, but I have consciously put myself in the habit of rolling the headlight control knob forward one click for daytime driving and all the way for nighttime driving.

 

That position is called "parking lights".
It is intended to be used when your vehicle is in a dangerous position and unable to move.......along with the 4-way flashers.
Having the headlights OFF allows the "marker lights" to stay on longer.

 

Australian PRIUS does it completely differently (like lots of things) - we don't have an OFF switch.

It looks like your OFF turns everything OFF - which would be great in a Drive-in Theatre, or parked waiting quietly for someone with the A/C on.


+++++++++++++++++++++++++++++++++++++++++++++++++++++

Mine are like this - no OFF:

 

Here in the UK we don't have the off or DRL positions on the switch, just Auto, side/parking lights and headlights. DRLs are on in daylight driving in Auto position and go off with any of the other two switch positions.
This renders the UK Prius not good for undercover surveillance operations