I did a search and didn't find anything about this on the Gen III Prius, nor did I see it on Toyota's website about the specs. I assume the 2010 Prius does not have auto-dimming side mirrors, only heated mirrors. And the only auto-dimming mirror is the rear view mirror inside (for the IV & V models). But just to clarify, does the 2010 Prius have the auto-dimming side mirrors in the US? If not, do the JDM mirrors have that option? It's not a deal breaker for me, but all of my cars except for my truck, has auto-dimming side view mirrors and they do come in handy and I've gotten used to it. That's all.
I have Prius 2010 IV and it only comes with auto-dimming Rear View Mirror. Yes, I prefers having auto-dimming side mirrors, but I do not see that an option.
I don't know if all have them, but I have a III with solar and the heated mirrors are activated by hitting the rear defrost button. Works great!
It is very easy to tell. In the early morning, when you back your vehicle out from garage, if the mirror seems dark, it has auto-dimming (since the front is dark, and the back is bright).
Heated side mirrors, activated when pressing the rear-defrost button. Auto dimming only for central rearview mirror.
Please let us know, If there is an Aftermarket Auto Dimming Side Mirrors available. It helps at night.
I just tinted my front side windows 35% that made a signifcant difference with the headlight glare from the cars behind you at night. It doesn't hinder my view at night at all (my truck is has 20% on the sides and 50% on the windshield, and that's dark to drive at night) so there's no effect on the Prius except less glare now from the side window tint. Just an FYI for those interested.
