I have a track light operated by a three way switch. Yesterday it didn't come on anymore. After taking it down I found that there was power in the wires but the only way the switches would turn the light on and off is if i connected one wire to the ground not the white neutral. I connected a lightbulb with a simple two wire cord to the wires in the box. It didn't work when connected to black and white but did when connected to black and bare wire, ground. Nothing electrical has changed anywhere in the house. Any thoughts?

 

Sounds like an open neutral. You need to check connections in boxes downstream of the switch that are on the same breaker. You can't know that until you have checked all the connections, tested screws for tightness, moved any backstabs to the screws, and removed and replaced every wire nut after first looking inside for corrosion.

 

You have lost a neutral connection somewhere in the circuit.

Do not use the ground to get this to function as you can create a serious shock hazard.

 

Your title --- actually it's not.

When checking for voltage with a meter -- the checks are normally done between the *hot* & *neutral* wires.
However, you can check for voltage between the *hot* & *grounding* wire --- between the *neutral* & *grounding* there will be no volts measured.

In your case , which is why the light worked when connected to *hot* and *ground*

Reason being the *neutral* & *grounding* wires are at the same potential electrically. The difference being , the white *neutral* wire is deemed to be a current carrying conductor in normal operation of the circuit.
The green or bare copper *grounding* conductor is only to provide a path for current to *ground* in event of a fault.


As the others have said -- it's because the *neutral* for the light fixture is open somewhere.

 

Thank you, that makes sense, I'll look at the connections at the two switch locations...

 

One switch for this light is downstairs, one is upstairs in that room. The black and white coming into that room closest to the light seem to be normal. I wired a light into those two wires at the switch and it works normally. Can I assume the wire from the closest switch to the box in the ceiling is the problem? everything else looks good. I haven't touched any of these switches or opened any of these boxes in 7 years.

 

You should check every neutral connection and splice between the point where you found the problem and the breaker panel, until you find and correct the open.

 

Is that a 2-conductor cable? If so disconnect and connect directly to the power in 2-conductor cable. No light the white is probably bad.

 

One switch for this light is downstairs, one is upstairs in that room. The black and white coming into that room closest to the light seem to be normal. I wired a light into those two wires at the switch and it works normally. Can I assume the wire from the closest switch to the box in the ceiling is the problem? everything else looks good. I haven't touched any of these switches or opened any of these boxes in 7 years.

 

If you're saying that you have a 2-conductor cable in one of the switch boxes that has power and a complete circuit when disconnected from everything else, then you have probably found the power feed to this switch set from the panel.

What other cables do you have in that box, and what cables do you have in the other switch box?

 

The switch nearest the light that isn't working only has power in power out to the non-working light. It ends at the non-working light. The other switch that operates that light is downstairs and has another switch for a different room in the same box with it. Neutrals are bundled together in that box. Everything looked normal in that box, no broken neutrals or anything. I disconnected the wires that go to the non-working light from the nearest switch and attached a simple two wire cord with a lightbulb on the end of it. When I turned the power back on the two switches functioned normally so I'm assuming the problem lies in the last run from the nearest switch to the non-working box/light and not somewhere else. All outlets etc on that same breaker show that they are properly grounded etc. Everything else seems to be fine.