Electrical Outlets showing Open Ground

[tycanis]

I am working on getting my home ready for sale because I am moving out of state for work.  Going through the outlets and installing GFCI outlets in the bathroom and kitchen I found that the bathroom outlets are showing 'Open Ground' on my tester.  Testing other outlets there are a lot of outlets showing this same thing.  However, looking inside the breaker box and opening some of these outlets up I see no issues with the wiring.  Everything is working on three wire instead of two with no 'dead man's grounds' any where.  The breaker box looks like all the grounds are attached.

Any suggestions on how to resolve this?  Any ideas where I could post this question instead to get some assistance?

Thanks.

[paddedhat]

A plug in outlet tester is an OK start, but it's time for the next step. Take an Voltage tester/ multi-meter  with digital readout, and test an outlet that allegedly has an open ground. What is the voltage from the hot to the neutral? How about from the hot to the ground? Is there continuity from the ground slot on the front of the receptacle to a bare ground in the box. Is there high resistance from the bare ground to the neutral at the outlet? All of these steps will isolate the facts. You may have anything from worn out receptacles to a wiring issue at a junction box somewhere. Hopefully it's something simple.

What year was the house built, and what was it wired with? Are there any really hacked up renovations, or other electrical issues?

[tycanis]

The house dates back to 1928.  All of the electrical was updated at some point.  When blowing in more insulation I found the old junction boxes and wiring.  However, the new wiring is what runs to all the boxes and from what I can tell most of the wiring NM 12-2 and maybe heavier to some location.

I will test some of the outlets but some of my concerns are that even after replacing some outlets they still show 'Open Ground.'  If it was the outlets shouldn't replacing them resolve the issue?

[Greg]

Check that the ground wires are actually tight in the panel, and also where there are any junction boxes.  As suggested, use a VOM to verify your tester results.  You may have to reach in and pull/tug wires and also tighten screws in the buss bars, so if you're nervous around a panel turn off the main breaker before reaching in there (probably good advice anyway).

Sometimes on older homes grounds are added by grounding to convenient metal plumbing which is also in turn supposed to be grounded.  Poor connections, corrosion and repairs that interrupt the ground can cause this kind of problem.  For instance a water heater replacement might include a dielectric union which might interrupt the ground by design.

[paddedhat]

The house dates back to 1928.  All of the electrical was updated at some point.  When blowing in more insulation I found the old junction boxes and wiring.  However, the new wiring is what runs to all the boxes and from what I can tell most of the wiring NM 12-2 and maybe heavier to some location.

I will test some of the outlets but some of my concerns are that even after replacing some outlets they still show 'Open Ground.'  If it was the outlets shouldn't replacing them resolve the issue?

Another clue.

It's common to find newer wiring that was run back to existing circuits. Often the "electrician" will assume that they have found a legitimate ground, since they are adding a new Romex to an old metal box, and the other wiring is metal clad cable. If I had to guess. I would say that the legitimate looking newer work you are finding, with properly utilized ground wire in the cable, and grounded outlets, is of little value, since the ground wire never made it back to the service panel. As Greg correctly notes, the other common issue is using the water supply system ( typically old galvanized or copper pipe) to establish a ground. It's common, but illegal, and it is worthless if one of the clamps is loose, or missing, or if a section of pipe was replaced with plastic.

[Spork]

(I'm not an electrician... take my advice with that in mind.)

Given what you've learned so far, wouldn't it be prudent to go back to those old junction boxes you've found and test the ground there?  That's closer to the source and let's you find out what you had before someone put "modern wiring" in there.