Diagnosing a busted microwave oven

Our GE Profile microwave oven is no longer heating. Everything else works -- the lights and fan come on -- but nothing cooks. I've Googled and come up with everything from blown fuse to busted magnetron (i.e. kaput).

It's elderly, and I'd just replace it, but it's a built-in over-the-range model, so that's not so easy or cheap.

Anyone have experience or pointers to useful diagnostic information? Also, recommendations for a decent but low-cost over-the-range replacement?

If the control panel, lights & fan work, and when you enter some time & hit start it makes fan noise and rotates the food (if applicable), then it does sound like a dead magnetron. This happened to an old (black with faux wood grain panels & lots of big knobs) GE microwave we had growing up...it looked & sounded like it was working, but the food was still frozen after it went "ding". A repairman came out, diagnosed it as a dead magnetron, charged my parents $25 for the visit, then left us to try to find an appliance sale.

Have you experienced any funny behavior? Like the LCD display blinking on & off, or the microwave stopping unexpectedly in the middle of cooking, or the control panel going unresponsive until you unplug the unit & plug it back in? If so, that would point to a faulty controller board...this happened to me recently, and is apparently a very common problem with modern microwaves.

In either case, it can be fixed, but doing so will require taking the microwave down anyway, plus the cost of the part & labor would likely exceed the cost of a new microwave plus delivery & installation costs (especially when Abt has one of their many free delivery and/or free installation deals going).

If you're up to the task, I've seen name-brand over-the-stove microwave/vent units on sale at Costco once in a while for quite cheap, but you'd have to put it up yourself. A friend of mine (one with very little prior home improvement experience) put his GE unit up himself using the included instructions, and it works & hasn't fallen down yet

You could call Young's appliances in Glen Ellyn. They are very knowledgeable and fix all kinds of appliances. I don't know if they will go to your area. The thing about appliances is that sometimes fixing them is not worth it. They fixed my dishwasher but said if it breaks down again its not worth fixing because of the cost of parts and labor. So you have to take that into account.