Generally, the most common causes of a failure to heat are:
- bad door switches or door switch mounts
- loose connection at the magnetron
- problem or loose connection on the control unit circuit board
- bad magnetron or other high voltage part (such as a shorted diode)
If it's a bad magnetron and your unit is within the magnetron portion of the warranty (usually 5-9
years) but out of the original full warranty (usually 1 year), then
your manufacturer will cover the part cost, but not the cost to visit
you or the labor charge to do the work.
If you or someone you know decide to look into it, we have critical safety information, info on door switch diagnosis and replacement, and disassembly information at our site, and our link is at our listing here on FixYa:
http://tinyurl.com/yzjozkWe're happy to help and we appreciate your thoughtful rating of our answer.