I am having some sporadic electrical issues here that comes and goes with no patern. Its really quite random when it happenes.  There are times when we try to use the deep fryer and when we turn it on the lights in the house will dim and the light in the frdge will be so dim it is barely lit. There are times when the wife will turn on her treadmill and every step she takes will dim the lights and then get bright and dim and bright and so on.  We have also been having trouble with the satellite box randomly turning off. Well today we were having issues with the satellite again. Well I happen to be in the kitchen and heard the fridge kick in and atr the same time it kicked out the sat again. I ran and grabbed my meter and headed for the breaker box. I checked the main lugs and had 103V on one leg, and 137V on the other leg. I never gave any thought to check across them to see what I had.  I went across the road to the machine shed and tested that box. I had 121V on both legs. Went back to the house and still had low voltage on one leg. I turned off the main breaker and tested again. It was a little better but still not right.  I turned the breaker back on and now everything is back to normal again. I was really leaning toward the transformer out on the pole until I checked the machine shed and it was all good. Now I am kinda wondering if my main breaker is getting a short in it for some reason. Is there anything else i can check for if it happenes again?

Sounds like a floating ground. With unbalanced voltage there Is a break in the neutral and/or one of the hot legs. Do you have underground service to the house? Also, if an overhead feed squirrels could have damaged the insulation allowing one leg to drain to ground.

I had a similar problem. Turn on the coffee maker, kitchen lights went dim. Cause was underground feed from transformer to meter had deteriorated after 26 years. Feed was directly buried in 1975, not in conduit. Vibrating at 60 Hz in rocky soil all those years had worn through the insulation. Replacement feed by electric company was run in conduit.

First is to have electric company to check incoming line. They can determine if problem is upstream or downstream of meter. To replace the main breaker the electric company will need to pull the meter. Depending on location you may need a permit  or licensed electrician to replace the main breaker if that is the problem.

Sounds like an open neutral at or ahead of the location with the 103/137 reading.

No this is all overhead wire. We had an electrician out a few years ago and replace everything from the meter on the pole to the house as well as to the machine shed across the road. It was all that braided rope style wire from the stone ages. For some reason though he only went to the hose. He didnt replace the wire running down the side of the house and into the service panel. I wonder if something happened to that section of the wire.

Not replacing the wire from the weather head to the breaker panel is a possibility for the problem. If that is the case be careful around the conduit running down the side of the house. If the conduit is not grounded then there is a situation of it being hot, and is an electrical hazard.

Even though the weather head is positioned to resist rain, the insulating grommet will deteriorate over time allowing moisture to intrude into the interior of the conduit, never completely drying out. And if the wire that was replaced needed it, then the section in conduit is probably worse off than the section  that was replaced.

Replace the weather head, conduit and lead-in wire, and for good measure the main breaker at the same time. Make sure that an adequate drip loop is  in place at the splices before the weatherhead to prevent water intrusion.

Need a laugh? There is a weather head but the wire is exposed. There is no conduit. This is an old house that was built before electricity was available.  This house was electrifies in the 40's and it was all knob and tube wire. We have replace most of it bu t here are still a few places where we havent gotten.

Then best approach is start upgrading to NEC standards from the splice in the overhead to the main breaker. Then with all panel breakers off cycle one at a time ‘on’ and check leg voltages. There could be one branch circuit causing the imbalance.

A question, what brand and age of the breaker panel? If it is a Federal Pacific it is a house fire waiting to happen.

I’m in the process of rebuilding a 50’s house. It will be a complete rewire with all walls taken down to the studs. Still has screw-in fuses, to be replaced with Square D panel. Finding taped one-to-three splices in the ceiling was a bit disconcerting.

Its all square D that we had put in 19 years ago when we remodeled what we could before moving in. The rest we have just been picking at over the years as funds would permit

So the main breaker should be GTG. That gets back to the upstream portion of the wiring that hasn’t been replaced as a starting point.

There's your problem.
The leg that is only 103 probably has corrosion upstream. Check the voltage before your main breaker and after it as well. It could be a bad main breaker.

Anytime there is more than a 5% difference between the legs, you need to fix it.

In the mean time, move the treadmill breaker and the deep fryer breaker to the 137 volt leg.