AC outlet voltage at 78v.... that's just weird

Discussion in 'General Technical Questions and Answers' started by W7UUU, Nov 13, 2017.

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  1. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Just started digging into this today - one of the circuits in my new place (in the garage) measures 78 volts hot to neutral!! All the other circuits in the garage read correctly. I only discovered this a short time before leaving the new house and didn't have the time to trace the Romex back to the panel. I do know there are a number of GFCI breakers in the panel.... but not sure if this circuit is on one of them.

    I cannot figure how a circuit could be at 78 volts AC.... could maybe a bad GFCI be what I should be looking for? Something else? ZERO volts or 120 volts I can deal with - 78 when it should be 120 doesn't register...


  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Trace the circuit back to the panel.
  3. KC8VWM

    KC8VWM Ham Member QRZ Page

    Could be an oxidized connection or faulty breaker. You can try pulling the breaker from the panel and reseating it back in place again. That can sometimes clear things up. Also check the wire going to any screws on the breaker and ensure these wires are screwed on tight. I often found situations where people have neglected to properly tighten screws on several occasions.
  4. KF5FEI

    KF5FEI Ham Member QRZ Page

    Could be a bum neutral from the utility pole.

    Pull the front off the breaker panel and see what you get right at the main breakers to neutral.
  5. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    I plan to - but the Romex is well hidden so will have to use an electronic tracer. I just ran out of time this afternoon otherwise would have started there. Just really odd that it's not just "zero volts". That leads me to VWM's post:

    That's my best guess: I'll bet this funky circuit is on one of the numerous GFCI breakers that's gone to heaven.... but alas will have to wait until next weekend - I'm on the road all week pretty much (unless something changes)

  6. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    No, I don't think so. No other such circuits in the rest of the garage, the house or the barn. A glaring thing like bad neutral would affect everything - not just one circuit. This is very localized to a single circuit: I'm betting bad breaker.

    I just can't think of what else it could be. Wish I had more time there today - I'd love to have another hour or two to dig in deeper. Never seen something like this before.

    N3AB likes this.
  7. KC8VWM

    KC8VWM Ham Member QRZ Page

    Not if all the other branches from the same panel are working fine and are reading the correct voltage. I understand it's just one leg coming from the panel with the low voltage problem.
    N3AB likes this.
  8. N6QIC

    N6QIC Premium Subscriber QRZ Page

    Hi Dave, I found some interesting answers to your question on this page.
    K2CAJ and W7UUU like this.
  9. KW5KB

    KW5KB Premium Subscriber QRZ Page

    I'm guessing that with any load connected, that goes down even more, likely (hopefully) to zero.

    Most likely a bad breaker contact, bad GFCI contact, or bad connection somewhere. I would be suspicious of any spring contact, back stabbed connections, but even screw terminals can get loose. Also be on the watch for any aluminum wiring.
    W2VW and N3AB like this.
  10. WD3N

    WD3N Premium Subscriber QRZ Page

    It was a dark and stormy night.
    The lights in some of the rooms (incandescent at the time) went dim.
    I had a flickering issue earlier that I had never solved .......until now .
    The neighbor and I share a pole transformer .

    I went outside and looked at the transformer using a good flashlight ...I saw one of the hot leads had
    fallen out of the splice connector.
    I opened all the breakers on the phase that was dead and called the power company.

    Next door I saw an HVAC truck at the neighbors.
    I went over and told him what had happened .
    They had low power to the furnace.
    I had him move the breaker for the furnace to another space ... heat again.

    Their electric hot water heater was providing a path to the other phase at a reduced voltage.
    The Power company made repairs and all was good again...

    It was still dark and stormy night tho.......
    K5ITM, K9ASE, KQ9J and 1 other person like this.

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