YESTERDAY I WANTED TO PRE HEAT , SO i PRESSED PRE HEAT BUTTON .AND CLOSED THE MICROWAVE. TO DAY WHEN i WENT TO USE THE MICROWAVE IN THE USUAL MANNER BY PRESSING MICROWAVE BUTTON AND ADJUSTING THE TIME OF 2.3 MINUTES THE WATER DID NOT HEAT UP.SUBSEQUENTLY I TRIED ALL PERMUTATION AND COMBINATION WATER IS NOT HEATING UP. WHAT COULD BE THE PROBLEM. MICROWAVE IS COMPLETING ALL FUNCTIONS EXCEPT HEATING