Chosen Solution
Intermittent problem: sometimes the magnetron will keep running after the cook cycle. The interior light, fan, and turntable all turn off at end of cook cycle, but magnetron will keep going and keep cooking food hotter and hotter until we open door – magnetron stops. Close door again, the magnetron will keep going, but still light/fan/turntable stay off like they are supposed to. Thought it might be the power relay (that feeds the magnetron) sticking…but I reason that, since the relay is NO (normally open), it would have to be fused/welded to stay shut. And if it was welded shut, it should be a permanent problem, not intermittent. Right?Thought about door switches too, but I’ve tested every possible combination of the three door switches being activated/deactivated and can’t get it to repeat. I often hear of bad/dirty door switches causing light/fan/turntable to keep going after cycle…and that is something I can reproduce just by a certain combination of door switches. Magnetron alone, via door switches I can’t reproduce. So, not door switches as the problem? Any thoughts?Schematic:
Hi, What is the model number of the microwave? Did you check the N.C. door switch is operating/releasing OK? Make sure that the door latch operating levers are correctly operating and releasing all the switches when the door is open/closed. A lot of ovens have 3 door switches, 2 x N.O. and 1 x N.C. When the door is shut the N.C switch opens which allows the HV circuit to function by removing a short circuit from around the HV transformer. When the door opens the switch closes again and short circuits the HV transformer preventing the HV circuit from powering the magntron. This is an inbuilt safety mechanism designed to prevent harmful microwave radiation (produced by the magnetron) from escaping out of the oven through the open door.
