The first thing I can think of is the microwave has a build in ground fault interrupter (GFI) or the unit is looking for a ground wire. Although the neut. and ground wires are tired together in the breaker box, they serve two different purposes. The neut is the return for the hot wire, and the ground is a safety wire incase the neut is open. The ground also ties the microwave case to ground and provides shielding for the electronics and the megatron (microwave transmitter). It is also possible that the hot and neut wire in the box are switched, and the microwave electronic's are sensing this and shutting it down.
David S.
:This earth grounding was talked about before so I hope I can ask this question. I purchased a new microwave oven. When pluged in a receptical without a earth ground (using an addaptor) It shuts down as soon as you push the start button. When you take the microwave to a room with a grounded receptical it works. I tryed to tie the nutral to the ground screw in the receptical (because the earth ground and nutral is the same in the braker box) it still does not work. Is there some fix besides running a earth ground to the receptical? If this question is out of line please tell me to go fly a kite!
:Thanks Steve
Steve:
The GFCI is the only thing I can think of that would made a microwave act like this, but every answer I come up with asks another question. This guy checks the current in the black (hot) and white (neutral). As long as the two currents are balanced, there is no fault going to ground (green or bare wire coming out of the wall), and if they are not equal, then current is going somewhere it shouldn't and the interrupter interrupts. You might have a mis-wired recepticle, returning the current to neutral via the ground wire, which is connected to the neutral at the fuse or breaker box, bypassing the current sensing couls of the GFCI.
Here's what I would do:
1. Remove power from the outlet by means of fuse or circuit breaker.
2. Remove the recepticle from the wall, and check the following:
The black wire(s) from the wall connect to a brass screw on the recepticle, correstponding to a narrow slot on the face where the plug is inserted.
The white wire(s) connect to silver (colored) screw, corresponding to the wider of the connector slots.
The bare or green wire(s) connect to everything elsse metal in the box, and are connected to the big grounded connectors on the front of the recepticle, this may use the screws that mount the recepticle. If the current were returning from the black wire through the bare or green, the GFCI wouldnt see a balanced amoutnt of current between the black and white, and would shut the device down, thinking there was a ground fault.
Lewis L.
1. Remove the fuse or opeerate the circuit breaker to remove power from the circuit.