Replies

1. 
   WorkshopJon | Nov 29, 2003 10:58pm | #1

   Wcg,

   If it is wired to code, you should be able to look at, trace, and inspect every connection as that circuit makes its way to the breaker box.

   That would be a start.

   Jon

2. 
   domermatt | Nov 30, 2003 12:00am | #2

   Could also be an open neutral. I would do what Jon said, trace the wire back to the source.

3. 
   CPopejoy | Nov 30, 2003 12:30am | #3

   Bill,

   There are several possibilities.  Each one starts with a question...

   First, did you use a regular multi-meter (digital voltmeter, digital multimeter) to make the measuement?

   If you used a DMM or similar instrument, it may well be that the cable you're testing is not energized.  It's possible that the voltge you measured is an artifact of the high impedance of the meter and electric charge that has "bled over" to the cable you're testing from a live cable running alongside. 

   This is called "phantom" or "ghost" voltage--i.e., votage that's the result of capacitive coupling between an energized cable and the unenergized cable that you're measuring.  There's voltage there, but virtually no current. 

   The best way to differentiate between true and phantom volatge is to use a tester that has low impedance, like a solenoidal model (the Wiggy is the classic, but the Ieal Vol-Con is my choice, as it also is a continuity tester).  Another way is to put a load (like a light bulb) across the hot & neutral, and using your high-impedance meter, measure volatge across hot & neutral.  The load will drain the capacitive voltage (essentially static charge), and then the high impedance meter will give a true indication of voltage.

   Ghost voltage is the most likely cause, because the cable to the outside outlet is dead due to a tripped GFI.  Because you mentioned that it was an exterior plug, I assume it isn't a GFI receptacle outlet.  It may be protected by a GFI inside the house or by a GFI circuit breaker.  If not a GFI breaker (evident from the "test" & "reset" buttons on it), go on a quest to find the GFI receptacle.  Could be anywhere, I'd look in the garage and bathrooms first. 

   If it's not a GFI and ghost voltage, second queston: how did you measure that 70 volts?  Was it across the black conductor (assumed hot) and the white (assumed neutral)?  Or hot to ground?  What about the voltage from neutral to ground (i.e., grounding conductor)?  We need all these measurements, made with a low-impedance meter or tester.

   There are several possiblities for a "real" 70V reading from hot to neutral.  One is an open hot, another is a mis-wire (load in series), another is an open neutral on a multi-wire circuit.  Rather than go into each possibility, I suggest that you report back, and we'll go from there.

   I'm assuming that you know how to safely make voltage measurements of line voltage.  I recently took some formal electrical safety training, and one point made  was that in the U.S., more people are electrocuted by 120V than by all other voltages together.  A lot of people are pretty casual working with household electrical wiring, thinking that 120V line-to-ground is nothing to worry about.  Not so--it can kill.  And when troubleshooting, it's easy to forget what's hot and what's not.  So work safe.

   Cliff 

1. 
   patepluma | Dec 01, 2003 01:08am | #4

   Dear Cliff-

   Wow- Sounds like you are an expert in this area!!  I will go and safely do some more tests.  I did try and hook up a light bulb to the two wires and nothing happened.  I thought that if it were giving 70 volts, the light would illuminate, although not too brightly.

   I did use a Digital meter.  I think you nailed it, with your "ghost" current.  I will look for a GFI too, although I don't believe there is any GFI system (s) in the house.

   Many THanks!

   Bill