Mercedes-Benz 2007 SLR Mclaren Operator's Manual page 199

Controls in detail
Automatic climate control
Activating
Turn the SmartKey in the starter switch
to position 1 or 0 or remove it from the
starter switch.
Press button T ( page 188).
The indicator lamp on button comes
on.
198
Deactivating
Press button T ( page 188).
The indicator lamp on button goes out.
The residual heat is automatically turned
off:
when the ignition is switched on
after about 30 minutes
if the battery voltage drops
if the coolant temperature is too low