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P.J.
P.J., General Contractor
Category: Electrical
Satisfied Customers: 747
Experience:  Various skills in all areas of construction allows me to help others solve their problems.
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hard wired my new dishwasher to existing circuit shared with

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hard wired my new dishwasher to existing circuit shared with garbage disposer. when energized, the disposer works but dishwasher doesn't. tested energized circuit with voltage finder and voltage is present at dishwasher. disconnected hard wiring and instead wired dishwasher to 3-prong power cord. plugged cord into different circuit and dishwasher powered up. checked junction box of dishwasher-disposer circuit and found no issues. is it possible that the dishwasher circuit is miswired with black lead actually neutral? I hesitate to simply reverse the connections to find out. how can I test with multimeter to solve this mystery?

Legacy Built :

I suspect your dishwasher is connected downstream of the disposer wall switch and the circuit only received power when the wall switch is turned on. If your disposer is not controlled by a wall switch then let me know and we'll try to narrow it down.

Legacy Built :

I may not have fully understood your description. When you mention you tested the energized circuit did you mean as connected to the disposal circuit or after you switch to the power cord?

Legacy Built :

Also, when connected can you describe where you tested for power at the dishwasher?

Customer:

the two are wired separately on the same circuit. the switch controls only the disposer.

Legacy Built :

Ok. So with your meter, testing between the white and black, you do have 110 volts at the location where you are connecting your dishwasher no matter what position the switch is in?

Customer:

the energized circuit was tested for voltage at the dishwasher junction box with a voltage finder which indicated that voltage was present at the dishwasher mounted j. box

Customer:

let me confirm that

Legacy Built :

Ok

Customer:

voltage varies between 100 &102 a/c v

Legacy Built :

Ok. Then that is why the dishwasher isn't working on that circuit. Most appliances will not operate below about 110 or so. You may have a loose or corroded connection somewhere or a nail through a wire. I would start at the breaker and try to determine if that is the problem.

Customer:

meter is Radio Shack Cat. # XXXXX I assume it's accurate.

Legacy Built :

I'm sure it's accurate. You could always verify by testing another circuit.

Customer:

Tell me if I'm thinking right. since the disposer works fine and the 2 machines are wired separately. the problem is probably between the junction box -where the 2 separate - and the dishwasher-mounted j. box, meaning I should replace the romex between those 2 j. boxes. Right or not?

Legacy Built :

I apologize but I still don't quite understand what you mean when you say they are wired separately. Do you have one power supply entering a single junction box and then two separate wires leaving that box to each appliance?

Customer:

yes

Legacy Built :

Ok. The disposal doesn't care too much if the voltage is low so my guess is that it is operating on a low voltage as well. I suppose if you test the voltage at the disposal and it is above 110 then the problem may be in the romex that you mentioned earlier.

Legacy Built :

If you test the voltage at the disposal and it is low as well then the problem is somewhere else.

Legacy Built :

118 to 123 volts is what you actually need to your circuits to ensure nothing gets damaged.

Legacy Built :

Anything electronically controlled will not live long outside those voltages.

Customer:

Okay. I'll rate you xlnt and get back with you if the problem remains unsolved. How's that sound?

Legacy Built :

That sounds fine. I'll be here if you need further assistance. Don't hesitate to let me know. Thanks, XXXXX XXXXX P.J.

Legacy Built :

Talk to you later.

P.J. and other Electrical Specialists are ready to help you
I would say your thoughts are correct regarding the romex. It sounds as though you are close to the solution. Keep me posted. P.J.
Your voltage reading from neutral to ground could be normal.

There are many reasons for voltage to exist in this condition.The most likely reason is a false reading on your meter. Digital meters do not handle this test well.

Other reasons are induced voltage, loose or corroded ground, reverse wiring in plugs, etc.

It can be difficult to narrow that down. P.J.

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