Pierre - Start your smart and drive until the engine is warmed up to operating temperature. With you car in PARK and running above idle, ~2000rpm, measure the voltage at the 12V recepticle in your car with an analog meter. It should be below 14.5 VDC and be steady. Switch the meter to the A/C scale and check for ripple. If AC is present there could be a problem with the alternators voltage regulation or unrectified AC causing the lamp failure. Just a guess!!! Good Luck!!!