there is no separate lights for up/down temp if you are talking about the back lighting. something must have come loose inside the button to block the light. all 3 are the same, a bulb in the center throws light in all directions.
you need to "carefully" figure out how to snap off the cover to see what is blocking the light
also the light bulbs are NOT all the same, the 3 hvac knobs and the "rec" and whatever buttons under them use the long lights.
the center display uses two short fat "socket" bulbs and the mode/next buttons use a short "skinny" socket bulb, as does the rear power window control uses the same bulb
also all those bulbs are not cheap to replace, they are something around $4-$6 each for them
i just replaced almost all of those on mine at toyotapartsdeal.com
Part No.: 90010-09019
BULB
$2.81 2 $5.62 - hvac knob/rec button bulb
Part No.: 90010-09018
BULB
$2.81 1 $2.81 - mode/rear power window button bulb
Part No.: 90010-09017
BULB
$2.81 2 $5.62 - LED display backlight bulbs