If the temperature gauge moves up to just below the red zone, you must first switch off the air conditioner, then turn on the heater on the highest and hottest setting. In this way, a part of the heat is withdrawn from the engine and helps in heating. After that, you need to look for the nearest service station with a mechanic in order to repair the malfunction. If this is not possible, you should contact the Road Service. This means that the correct answer is all the above.