Model #R-3A57 will not operate until light

There is a short in the door interlock or related wiring.

Door and/or latch assembly is out of adjustment. Some can be adjusted internally. After making any repairs on a door or latch, the oven needs to have a leakage test done.

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

Sounds like on reassembly you reversed wires to door switch.
switch might have letters C NO NC (common, normally open, normally closed) one wire goes to C common, the other to NC normally closed. Try reversing the wires.
If you use meter measuring continuity meter on C and NO should be high resistance until you press switch.
meter C to NC measures low resistance until you press switch then measures high or infinity (open)

This seems to be a defective door/interlock switch. There is a minimum of three interlock switches inside the oven that operate by the catches on the door. By opening the door or slapping it you are causing the to make connection.

As I understand your trouble, your 7 year old microwave does not heat.

I have found the most likely reason for this trouble is a burned door safety interlock switch.

To fix this trouble, remove the cover, find the switch opposite the door hinge. Test the switch for proper operation. You will need a continuity tester or a volt/ohm meter for this.

Let me explain what happens and you will be able to apply this to your situation. When you close the door these switches tell the oven the door is closed and it is ok to turn on the magnatron. If the switches are burned, they cannot tell the oven the door is closed - door not closed, no magnatron, no magnatron, no heat.

Why do they burn? Do you open the door while the oven is in operation? If you do, there is a spark at the tiny micro switch contact and they start to burn. Eventually, they will not close properly.

You can find replacement parts at a FixYa.com advertiser or a appliance parts store in your area or at www.repairclinic.com

The next most likely problem is the start capacitor. This is the silver can inside. Please do not servic this item unless and until you understand the danger associated with it.

This device stores a very large electrical charge. Modern capacitors are supose to drain off the power after a certain amount of time. Some say it is OK to drain the opwer by shorting with a screw driver to ground. Frankly, I'm not a fan of this method. Please try the switches first ... if that doesnt work, post a note here and we can go to the next step.

I hope this solves your trouble and you are able to get your oven back in operation. If you will search this problem here at FixYa.com, you will probably find other ideas from other volunteer workers.

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the door interlock switch needs adjusting or replacement

That would be a defective secondary interlock (lower door switch) or its mount.

Door switch or mount trouble is usually 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.

We have the service manual for this model and have uploaded it to our site here to help you.

You will need the free Acrobat Reader to view or print it in case you don't have it.

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

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

This is usually caused by either a bad door switch or a loose door switch mount (which are pretty simple problems to fix).

Door switch or mount trouble is usually 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:.

We have uploaded the R1480 service manual to our site here to help you.

If yours is a different model, please reply back.

The best place to order Sharp parts is Tritronics.

You can also call them at 866-779-5835.

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

This is usually caused by either a bad door switch, a loose door switch mount, or a problem on the control panel.

Even though a door switch clicks, it may still be bad inside. Its continuity must be checked.

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.

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: http://tinyurl.com/yzjozk

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 and we appreciate your thoughtful rating of our answer.

William E. Miller, AS-EET
[email protected]
http://www.microwavedisplay.com