Question about Sharp Microwave Ovens
A microwave can be dead for many reasons.
It may be the fuse, which is usually located on the floor of the oven behind the control panel or between the door switches.
If the fuse is good, it may be an open thermostat or thermal cutout (TCO) / thermal fuse on or near the magnetron or on top of the cavity / body of the oven.
If it goes dead for a while during or after cooking then comes back on, the magnetron is probably overheating and causing the magnetron thermostat to open.
Then when it cools, it closes the circuit and allows power through again.
When checking thermostats, if it has a hood fan thermostat, that should read open, as opposed to the others, which should read closed.
If it went dead almost immediately after pressing the Start pad, that's usually a shorted high-voltage capacitor.
If it went dead a few seconds after pressing the Start pad, that's usually a failing high-voltage transformer.
If it goes dead or blows the breaker when you plug it in or open or close the door, then there's a problem with a door switch or door switch mount.
If it's intermittent or random, it may be a bad connection, usually on the control board or a loose fuse holder, or even an intermittent fuse.
You should do a continuity test on the fuse while it's in the holder (with the microwave unplugged, of course) then turn the fuse by hand or take it out and put it back in, then test it again.
If you remove the fuse, then press the meter leads against the ends, it can allow internal contact to be made and make a bad fuse appear to be good.
If you or someone you know decide to look into it, we have critical safety information and disassembly information at our site, and our link is at our listing here on FixYa.
There should also be a "mini-manual" hidden inside the unit behind the control panel or hidden on the left side behind the grille, which is very helpful when troubleshooting & testing.
You can probably find exploded views and order parts by entering your model number here at the Sears parts site.
The best place to order Sharp parts is Tritronics.
We have the full service manuals for this series of ovens and have uploaded them to our site here and here.
We're happy to help and we appreciate your thoughtful rating of our answer.
Posted on Jul 13, 2008
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