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Tyler Z.
Tyler Z., Appliance Doc
Category: Appliance
Satisfied Customers: 81121
Experience:  9+ years being an appliance technician with factory training.
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The oven light on my kenmore microwave Model#721.62642200 has

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The oven light on my kenmore microwave Model#721.62642200 has been acting up for yrs.. It wouldn't come on when door was opened, but if you pushed on front of microwave just under the digital displace, it would come on. Sometimes stay on sometimes not. So I decided to see what might be the problem. I found the schematic and traced the wiring from the lamp to a relay RY1. I found that one of the terminals wasn't soldered good. So I soldered it. Ya, the light works perfect. Now the microwave doesn't. What might have happened? The only plug that came into question was the RY2. It plugs in any direction. It looks right to me now. I might have had it wrong at first. Any ideals?
Hello, and thank you for using this service. I'll be helping you with your problem today.

So what happens with the microwave exactly when you try to start a cycle? And you didn't happen to flip the 2 wires on the RY2 relay plug did you? If you reversed them, that could cause this problem.

Customer: replied 3 years ago.

Maybe


 

Try reversing the plug to start, That could be the cause of your problem. If not, then please try to describe what you are seeing when you try to start a heating cycle like what happens on the control panel, and what do you hear?

Customer: replied 3 years ago.

Nothing happens when I push any buttons. Just a : sign in the window. I did try to reverse. Nothing happened. Looking at the wiring and it looks to be right. In the schematic it said a -F4- would show in window if wired wrong. But that didn't appear.


 

OK so if nothing happens when you press any button, the issue is with your touchpad. Make sure the ribbon cable that comes from the touchpad is securely plugged into the control board. If so and you don't even get a beep when you press any button, you'll need to order and replace the touchpad itself.
Customer: replied 3 years ago.

What would have caused the pad to go out? Ribbon cable snapped in tight.

That's really impossible to know, but sometimes just bending and moving the ribbon cable around while working on the appliance can cause it to go bad sometimes.

Customer: replied 3 years ago.

Are you saying the ribbon cable is broke?

Again, that's really impossible to know, but sometimes one of the little contact strands that runs through the cable can sometimes break internally inside the ribbon cable.

Customer: replied 3 years ago.

Your saying that has to be the problem. Nothing else could be the problem?


 

Well, not exactly. The only other possibility would be the control board itself. But unless you caused damage to the board when re-soldering the board, then the touchpad would be the problem. There is no way to test between the two, but if you didn't damage the board then the touchpad is the only possibility.

Customer: replied 3 years ago.

How do you mean damage the board? I just turned it over and put a solder on it. The soldering itself wouldn't have caused a problem would it. I just did a quick solder. I use to be a Tech. and know not to over heat a circuit.

It shouldn't damage the board, but overheating the board during a re-solder job or soldering multiple points that shouldn't be soldered can cause the board to be damaged. Again, there is no way to know which is is bad. if this were a regularly occurring failure without you working on the control board, then without question the touchpad would be bad. If you think that you may have damaged the board when you repaired it, then that throws in another possibility.

Customer: replied 3 years ago.

Thanks, XXXXX XXXXX a bad light was the better of 2 evils.


 

Aye. Unfortunately sometimes just working on an appliance can cause problem. I know that a few touchpad cables have gone bad while I've worked on a microwave or oven just due to the nature of heat causing things to go brittle.

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