Mercedes-Benz C-class Operator's Manual page 60

Note:
When in operation, the seat heater consumes a large
amount of electrical power. It is not advisable to use the
seat heater longer than necessary.
The seat heaters may automatically switch off if too
many power consumers are switched on at the same
time, or if the battery charge is low. When this occurs,
the indicator lamp in the switch will blink (both
indicator lamps blink during rapid seat heating mode).
The seat heaters will switch on again automatically as
soon as sufficient voltage is available.
If the blinking of the indicator lamps is distracting to
you, the seat heaters can be switched off.
Seats 51
Instruments Instrument Technical
Operation Driving Practical hints Car care Index
and controls cluster display data