Jenn-Air JMW2427D, Technical Education

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OPERATION
Microwave Combination Wall Ovens
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The first thing we need to do when discussing the microwave oven is tallk about the built in safety
system. Because of the microwave energy being produced by this oven, we need to be sure the oven
safety system is in place and operating correctly. The microwave needs to know whenever the door
is open or closed. To do this, there is a series of door switches that operate in unison and control the
operation of the high voltage system. This diagram shows the MW door closed and the safety switches
(Primary, Monitor and Secondary) operating as designed. Outlined in the diagram, the Primary
Interlock switch provides a circuit(contacts 1-2 closed) to the Appliance Manager any time the door is
closed. This circuit informs the AM that the door is open and the oven light should be on. The Monitor
Interlock Switch is your safety switch that will open contacts 1 to 2 when the door is open. If contacts
1 to 2 don’t open when the door is open, you would have a direct short through the Monitor switch to
the Neutral side of the line. The Secondary Interlock switch isolates the Neutral line from the L1 side.
When the door closes, the Secondary switch contacts 1 to 4 close and provide a complete circuit to the
Neutral side of the line. So the door switch circuit has to operate correctly before the microwave will
operate.
Just like the main oven, there are LOGIC circuits in a microwave oven. The LOGIC circuits provide
the Appliance Manager with information (in this case all three circuits OHMs resistance) from the
Magnetron and Cavity Thermistors and the Humidity Sensor. The Microwave Inverter also provides a
LOGIC circuit to the Appliance Manager but we will take a closer look at that later.
The main reason for this portion of the microwave oven diagram is to show you that certain things need
to be operating correctly before the Appliance Manager will even start a cooking mode.
Safety System & LOGIC Circuits - Microwave Oven