Customers complaint: No power. She informed me that she had mistakenly ran micro. with no load for about 30 seconds. I pulled micro. out of cabinet and found the magnetron thermostat to be open and replaced it. The magnetron showed continuity across leads and no short to ground. I checked air flow at blower and re-installed micro. After installing, I ran micro. with load for 5 minutes without incident. All seemed fine until a couple of days later. Customer called back with same complaint. Before I return to this call my question is should I have changed the magnetron assuming heat damage, or could there be another cause for this thermostat failure? I have never seen this model before, lots of extra electronic, relay boards ect. Any suggestions would be greatly appreciated.