In my E90 I have a REST button:
It seems not to work, when I press it, the LED won't light and the heating won't work. Could this be a defect fuse? And if yes, which one (could it be 15 and/or 67)?
From what I understand and how I've seen it used.
If the ignition is off it uses the residual heat from the engine to warm the car.
In order to validate my claim, turn your car off and hit the button. You may need to try it with the key in it.
Interested if I'm correct. Please follow up. :-)