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Had an instance before when I had a voltage while running on a treadmill. I flipped all the breakers and it seem to work again for a month and now it is back and now when we use a high load appliance like the microwave the voltage drops.

I tested all the breakers by adding a load and it seems it’s on one leg. And I tested the lugs and the voltage did drop with a load. Unfortunately the tested I am using isn’t digital and doesn’t display the actual voltage but the 120 light is completely off under load and only the 24v is light. The 120v light comes back on when the appliance turns off.

Is there a problem in the house on one of the circuits? Or does the drop on the lug indicate a problem before the breaker panel?

Thanks in advance for any advice.

Edit: I picked up a digital multimeter and now under normal loads the one leg reads 125-126 and other 115ish. With the microwave on it goes becomes more unbalanced 130v one lug to 110v on the other

Edit2: with the washer a full when agitates(using the motor) voltage dropped to 97v on one leg and the 140v ish on the other. Again coming in from the service line to the main breaker. That seems to be getting too much so I called in with the PoCo reporting a partial outage.

I bet I'm in a race with ThreePhaseEel to post this.

Call your power company NOW and report an outage

Specifically, a lost neutral.

My company came out in less than 2 hours on a Saturday. It will be free, and most likely they'll find a problem on pole or service drop. Just the same, helps to have the front off your service panel.

As you know, American houses get 240V power, but appliances are 120V, or half. What keeps the center centered is the neutral.

If you lose neutral, then each leg becomes biddlebooble, but the two legs still add up to 240V pretty much on-the-money. That means when one is under 120V, the other is over by the same amount. And the high leg can switch. This is what makes it an emergency: the significant overvoltage can blow out appliances and start fires.

At this point it seems like a partial failure, but it's likely to become a total failure soon. My power company just fixed one of those, our neutral was flapping in the breeze, but a neighbor's hot was nearly worn through from a bad termination on the pole and years of cable swaying just wearing it down.

Also, total neutral failures will act like partial failures, because they are still able to return some neutral current via earth to the transformer's ground strap.

On your main breaker, Are you checking at the connection of the service to the breaker or after the breaker? If after the breaker try turning all loads off and flip the main breaker 10+ times, this can reseat the hammers in the breaker. If measuring prior to the breaker call your utility and tell them you are having a service problem.