A question has been asked how to remove the wing mirror cover to indicator unit, on the Avensis T27 from 2009 to 2015.
Flat bladed tools are required like trim removal tools, but screw drivers will do. Starting from the top side, carefully insert the tool between the cover and black border, then gently lever away. 
Work around the the cover with another tool
I fold the mirror to work to tool down. Then firmly pull the top of the cover away and down. The cover will come away.
Looking at the inside of the cover, you can see why cover needs to be separated from the top -
These clip/tags are not accessible.
The tools I used to remove the cover.
Now looking at the uncovered wing mirror, the indicator is more accessible. I did not go further and remove the indicator, since it was fine.
Also looking into the mirror itself 
Notice the connections for the heated element.
Replacing the cover, make sure the black border is between the inner and outer lips of the cover, then push it firmly back in place.
Hopefully this will help those unfortunate to need to replace the indicator or glass.
Konrad
