I have a Panasonic NN-E548W microwave. The light stays on even if the cooking time has finished, (or even before it has been set). (I was going to add that the turntable turns also, but I have just discovered that this seems to have fixed itself). However, it was never cooking when in this state.
This all started after my lodger had a bit of an accident with a large liquid spill some months ago, (easily long enough ago for it to have dried up now), but I can't be absolutely 100% sure this caused the problem. Can anyone help please?

Mike Hodgson, March 2004

My panasonic microwave chrome (NN?? I believe) counts down and turns it self of at 37sec (so runs for 23 seconds exactly every single time) whether its set at 10mins or 1min after 23secs it switches off , well back to standby anyway, all displays are fully functional- works ok on convection/ combination etc just on microwave setting it has this problem!

Cheryl, January 2011

Sounds like a problem with the door or door microswitches. Recommend that you get a professional to check it. Microwave Ovens can still have live high voltage[4000volts] at the the capacitor even when disconnected from main supply.

SSEB, May 2004