Rear defrost won't auto turn off

[darrylj]

There are a billion posts everywhere when your rear defrost won't power on or heat, but I can't find any on how to diagnose or fix the following:
rear defrost comes on fine, heats fine, turns off manually fine, but never turns off with the timer. If you turn it on at the start of a 1 hour car trip, it's still on at the end of the trip.
2015 4runner SR5.

 

[mo_mo]

There are a billion posts everywhere when your rear defrost won't power on or heat, but I can't find any on how to diagnose or fix the following:
rear defrost comes on fine, heats fine, turns off manually fine, but never turns off with the timer. If you turn it on at the start of a 1 hour car trip, it's still on at the end of the trip.
2015 4runner SR5.

From the 2010 service manual that was floating around at one point:
The system automatically turns off when the back door power window is opened, or approximately 15 minutes after operation starts. For vehicles with an air conditioning system, there is a timer extension function which can operate the window defogger system for up to an additional 255 minutes.

HINT:

The timer extension function operates when the following conditions are met:

Ambient Temperature: 0°C (32°F) or less
Vehicle Speed: 31.1 mph (50 km/h) or more