If a 2009 Volkswagen Beetle displays a flashing coolant light when the engine is first started cold, do not allow the coolant to warm.
Using a DVOM, back-probe the signal wire. Set the meter to the A/C voltage scale and switch the ignition ON. A reading above .1V on the New Beetle will illuminate the light. With the meter still connected, open the coolant reservoir and clean the level probes with a flat tip screwdriver or similar tool and watch for the voltage reading to drop.
If the reading is above .1V on a New Beetle, the reservoir with the sensor will need to be replaced.