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Background: I'm doing some rewiring work in the kitchen. There were three circuits coming into a junction box that controlled the sink disposal, dishwasher, a few receptacles and a light. So I got everything the way I want, and the dishwasher circuit seems like it's dead. First thought is bad wiring, so I rechecked everything - no issues. Next thought, there's a GFCI upstream that I tripped while I was working (I've wasted a few hours on that problem before). But an ohmmeter check on the common/ground says no GFCI tripped. So I recalibrated my voltmeter and tested the line again and lo and behold, there is some power, but only about 20V.

Question: could the breaker really have gone bad while I was working on the junction box? Everything I know says it's possible but extraordinarily unlikely. I've even replaced a breaker before thinking it had gone bad, and it turned out not to be the problem after all. So before I do it again, is there anything else I'm missing?

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These kinds of problems are very difficult to diagnose without being on site. Rather than guessing at a single fix, let me give you a process to follow. Think of electricity as a closed water system, with hot water coming in and cold water draining out. What we are looking for is a leak in the system. I'd start at the breaker. Check the load screw to the ground/neutral buss. 120vac ok? yes, then we move further down the line to the next possible junction point. At each subsequent point, check your hot side to neutral and to ground until you find the point where there is no longer a proper 120vac measurement. When you find this point, if you have 120 hot to ground, but not to the neutral, you have an open neutral. Turn OFF the power and check the neutral to ground with an ohm meter. It should be very close to 0 ohms. If you see no voltage to either neutral or ground, and the neutral to ground is 0 ohms, then you have an open hot. Check the input side of the GFIC and the load side in a similar method. If you try to follow a very straight logic, testing the three possibilites at each point,(open ground/open neutral/open hot) hopefully you will find the culprit. Good Luck

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    Turns out the neutral was damaged behind the box, where I couldn't easily see. Thanks! – Rex M May 15 '11 at 17:55
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If I were to guess, 20V sounds like what you might see connecting the neutral to the ground. I'd double check the hot line to make sure it's properly connected at each point (dishwasher, junctions, breaker).

protected by Community Nov 24 '17 at 16:47

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