DIYbanter - View Single Post - Microwave oven -- Whirlpool MD365WH

Marcus Lindahl

hr(bob) wrote:
On Oct 8, 8:41 am, "William R. Walsh" wrote:
Hi!

If I open the door during the hot air function the oven runs for about
3-5 sec before it stops, therefore I belive that heating, fans and the
rotating plate is relay controlled by the microprocessor and that the
interlocks only shuts down the magnetron (I´m not sure though).
I've never seen a properly functioning microwave oven where *any* part
of the oven continued to operate if the door was open. It seems to me
like letting any part of the oven continue to operate might alarm the
end user at the very least.

However, I have seen a Sharp oven with a bad door switch that would
start its fan (and maybe the turntable as well) whenever the door was
opened and the oven was off. Replacing the one bad switch cured the
problem entirely, and the oven works fine to this day.

Or is it possible that glitching interlocks can cause all these
kind of erratic behavior, possibly confusing the microprocessor?
This is something that you should examine. However, please do consider
the fact that a microwave oven is easily the most dangerous appliance
you have in your house due to the high voltage. With its power cord
unplugged and the capacitor discharged, the oven will be
inert...unless of course, you drop it on your foot.

If that fails, I'd make sure that the sensors used in the cooking
process are clean, and I'd also consider cleaning the control board.
Many ovens don't protect it from food vapors and grease. If that stuff
got on the board, it could be shorting out and messing up all kinds of
signals going to the controller.

I don't think it would harm anything to simply wash the control board
in warm soapy water as long as you let it have a day or two in a sunny
window to dry out. Rotate it periodically so that a different side
faces the window.

William

I don't know that particular model, but sometimes the flexible ribbon
cable that connects the keypad to the main controller printed circuit
board has intermittent contacts. Have you checked this by reseating
the cable?

Hi,

Thank you for your answer.

On this model the cable that connects the powersupply -- control
circuit board is directly soldered on each board, there are no connectors.

I have tested with cooling spray and found that when I cool down the
microprocessor the oven starts to behave erratically. So probably there
is a problem with that one. The microprocessor is mounted directly under
the VFD, probably the heat generated by the display have killed the
proecssor after its 10 years in operation.

Kind regards, Marcus Lindahl