REST Mode
WARNING: This page is about a different car, the 2000 Mercedes-Benz C230. However, it is still accessible from the selected car via links, so may be relevant.
In Residual Engine Heat Utilization (REST) mode, the blower motor runs at low speed as the system maintains interior temperature according to selected setting.
The REST mode has an elapsed time of approximately 30 minutes. The footwell flaps are open, with defroster flaps in bleed air position. Battery voltage must be more than 11 volts and engine coolant temperature must be more than 122°F (50°C).
This mode is switched off when recirculation push button is pressed again, engine coolant temperature falls below 104°F (40°C), battery voltage drops below 11 volts, after 30 minutes have elapsed, or if ignition is turned on.