If you thought the smart had one heater, you'd be wrong.
Rear Window Heater
It’s two main functions are to clear the rear screen if it has fogged or is icy.
The button (1) is located on the safety triangle on top of the dashboard.
Operating the rear window heater is very easy, the ignition must be in position 1 for it to work. Press the button on the safety triangle and a light will illuminate to show it is on.
Pressing the button once again will turn the heater off and the light will go out.
The rear window heater automatically turns itself off after 10 minutes of operation.
It also turns off when the ignition is turned to position 0.
Heated Wing Mirrors
The electric adjustable wing mirrors also have heater elements built inside the unit.
As is the case with the rear window heater, the mirror heaters are primarily designed to disperse fogging and ice from the actual mirror.
The wing mirror heaters are activated using the rear window heater switch mentioned above, both come on and off simultaneously and automatically turn off after 10 minutes of operation. They turn themselves off when the ignition is in position 0.
In the smart cabrio, as there is no rear window heater so no switch, the wing mirror heaters are turned on with the ignition so are always on when the car is.
The two middle switches on the safety triangle (2 and 3) allow the heating of
both of the seats. The ignition must be in position 1 for them to operate and
both seats have a two stage heating system.
Each button has two lights to show the heat setting. With both lights off the seat heater is off. A single press will illuminate one light, this indicates that the heater is working on half power. A second press illuminates the second light indicates that the seat heater is working on full power.
Pressing the button once more will turn off both lights and the seat heater.
The seat heater will stay on until you turn them off manually or the ignition is turned off.
If the heater light illuminates for a few seconds and goes out, it means there is a fault in the system. Check the connections under the seat are pushed in properly and also check the relays are seated correctly. They are either located at the back of the SAM unit or under the speedo either side of the steering column.
Diesel Heater Booster
This is only available on the diesel smart. If you slide the heater temperature slider all the way over to the hottest setting a light will display on the dash. This means that the electric heater booster is activated, it is very much like a toaster element, as electricity passes through it, it gets hot. The fan then blows the hot air from the vents.
Added to newer smarts, it is installed to bring the engine up to temperature as quickly as possible. Warm engines are more economical and produce less emissions.
Nothing needs to be done to turn this heater on, if you have it, it will turn on when needed.
You may notice when you start you car from cold you hear a click every now and then from the SAM unit. You may also notice that the lights dim on each click before returning almost immediately to full brightness. This is normal behaviour and is just the heater drawing a lot of power before the alternator can boost the voltage.