I have a Whirlpool AMW545 built in microwave oven. The turntable continuosly runs with the door shut when the microwave is not in use. The turntable will stop rotating if the door is opened.

Look in your yellow pages for small appliance repair, or contact manufacturer for list of repairmen.

I'd look for a defective relay or shorted triac on the control panel circuit board. Either could cause this problem.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/david_29ad5d1dd86564b0

Hi,

Here is a tip that will help you to figure out what is wrong with your Microwave Oven....

Basic Microwave Oven Troubleshooting Tips

heatman101

/,..........

You probably have a bad door switch or door switch mount. See this file.

If your microwave oven doesn't appear to shut off when the door is open, you may have a problem with the door switch. The door switches, often referred to as interlock switches, provide power to the various components of the microwave. They are designed to interrupt the power when the door is open.
https://www.fix.com/repair/appliance/microwave/doesnt-shut-off/
https://www.youtube.com/watch?v=y2zIRmaaH0A

Turntable usually automatically switch off. If it is continuosly running check the related relay driving circuit.

It's possible that the module that produces the microwaves is failing. The parts are cheaper but the labor may not so get an estimate before deciding if it's worth repairing or replacing.

Check and replace the door safety switch.

Do not run the microwave with the door open. You will be cooked. Sooner or later, if there are enough microwave ovens, (and there are), everything that can go wrong with them will, eventually. There are several interlocking safety systems built into every microwave so that they won't work with the door open. Yours may have failed. I've never come across one, but that doesn't mean it can't happen.
It may only have a fault making the fan and turntable operate, which can sound like it's working with the door open. Either way, get it checked or get a new one.
This assumes that the microwave isn't actually supposed to do what it is doing under normal conditions or current programming. Refer to manual/instructions if unsure.:::Spiceweasel.au

all microwaves have 2 safety switches at least... but these are tied to a set of relays that turn it on, my bet is a sticking or stuck relay because you unplug it right and plug back in its not running?-relay ... if always runs driver transitors.