Question about Sharp R-340 Microwave Oven

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Hello, I have a model R303CW microwave. Table turns,lights work, fan works, control panel works. NO HEAT. I see only one fuse, so that must not be the problem. Any suggestions?

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The fuse you are referring to is usually the line fuse. If it were blown, the microwave oven would be completely dead. Since you HAVE power and the turn table, fan and lights all work, the line is not the problem.

If everything works, but the microwave oven does not heat, this is most commonly caused by a failed magnetron or internal thrmostat. The magnetron is essentially, the heart of the oven that produces the RF energy that is used to heat your food. In order to replace a defective magnetron, you will need to consider the following:

1. You will need to uninstall the oven from over the range in order to replace the part (you will need to do this anyway, if you decide to buy a replacement oven).

2. Ensure the oven is UNPLUGGED before servicing anything inside the cabinet and remove the exterior case in order to access the magnetron.
There are several websites that you can use that illustrate how the oven is assembled:
NOTE: If you've never repaired an appliance on your own before, a microwave oven is usually not a recommended appliance to start with. Some models can be rather involved in taking apart.
If the model number you posted this question under is correct, the magnetron replacement part number is 10794402. NOTE: This model also has an internal thermal fuse mounted on the magnetron that, if tripped, could give you the same symptoms. The thermal fuse acts as a fuse if the oven cavity or magnetron overheats. The part number is 59001951. You will need to remove the thermal fuse from the oven and take a resistance check across the component terminals to determine if it is good or not. A low resistance reading indicates a good thermostat. An infinite reading, indicates a blown thermostat and needs to be replaced.

I would recommend you check the thermal fuse, first as the replacement cost is much less than the magnetron.

Review the parts illustrations at the recommended websites to see if this is something that you may be able easily take apart and reassemble.

If you have any questions, please post back and let me know. I hope you find this information helpful.

CAUTION: DO NOT operate a microwave oven with the exterior cover off. The voltage inside the High Voltage network where the magnetron is installed can exceed 3,000 volts!

Posted on Nov 08, 2010


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