GE Advantium SCA1000.

I fixed this yesterday, using the solution posted here: http://forum.appliancepartspros.com/microwave-repair/4882-advantium-turntable-light-always-main-relay.html

Unplug the unit.

Replace the interior light using these instructions: http://www.instructables.com/id/GE-Advantium-Microwave-Halogen-Lightbulb-Replaceme/ The inside of my unit looks a bit different from the pictures, but the procedure is basically the same.

Additional info not in the procedure link above:

Remove the one screw at the top of the front control panel.
Slide the control panel up to disengage it, and pull out slowly (has wires on back)
There are four black rectangular things running top-to-bottom on the PCB board on the back. One of them is labeled RY1.
Tap on RY1 with a screwdriver a few times (very high tech). I actually tapped on all of them for good measure.
Reassemble, see if everything works now.

It took me about 30 minutes for the bulb and the control panel 'adjustment'. Everything is working now.

This solution worked for me (so far)! The only thing I would add is the control panel is the big box on the front right with all the buttons and knob. The whole rectangle portion of this will disengage with the removal of one screw and a slight pull up and out. I just flicked all the black rectangular things with my finger nail. I had to do it twice before it worked. Thanks for the great post.

Okay, got it.

This is usually caused by either a bad door switch, a loose door switch mount (which are pretty simple problems to fix) or occasionally a problem on the control panel.

Door switch or mount trouble can be caused by slamming the door or by opening the door while it's cooking without hitting the Stop pad first.

There are plastic mounts inside the microwave which hold the door switches and onto which the door latches lock when you close the door.

The screws on these mounts may be loose. If they get too loose, the switches will not be activated properly.

Sometimes it's a broken tab on the switch holder, allowing the switch to rotate just out of position. This tab can be hard to see, since it is under the bottom edge of the switch.

If you or someone you know decide to look into it, we have critical information on safety, disassembly and door switches at our site, and our link is at our listing here on FixYa:.

You can find helpful exploded view diagrams and order parts by entering your full model number here.

There may 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.

If you only need a switch, you can order a universal type from us for $5 postpaid.

If you think the problem is on the control panel, we repair these nationwide by mail for $39.95 postpaid in most cases.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

I tried the tapping RY1 trick, which worked for a moment, then the breaker flipped. After resetting the breaker the microwave appears fully dead. Is it worth replacing RY1 at this point, or is this now a new / final problem?

Not sure if what I tapped with my screwdriver was relay RY1 or what, but I tapped on everything that looked like a relay. Put it back together and it works! Excellent fix!