Can I check the voltage myself with a multimeter? If so how?
Agree with with Al...... But just remember the voltage reading will only be for that moment in time.
I suggest you talk to the other tenants in the 4plex.
See if they are having the same problem with light bulbs as you are.
I asked a question in an earlier post if you noticed if any incandescent light bulbs suddenly get brighter than normal.
With a loose service neutral conductor connection this is typical. The service neutral conductor carries only the unbalanced load back to the source, the utility transformer.
Example, say all Line 1 (L1) to service neutral loads equal 20 amps and all Line 2 (L2) to service neutral loads equal 20 amps. Then 0 amps will return to the source on the service neutral conductor. The two loads are in series with one another. If the loads are constant and do not vary the service neutral conductor could be disconnected and the two loads would continue to operate just fine.
But what if L1 to neutral load increased to 30 amps and L2 to neutral load remained at 20 amps. If the neutral has a good electrical connection back to the source then 10 amps will return on the neutral to the source.
Some simple calculations..... Lets keep it simple.... purely resistive loads. E = I x R
L1 to neutral load 30 amps. Find R (resistance in ohms)
120V / 30 = 4 ohms
L2 to neutral load 20 amps.
120V / 20 = 6 ohms
Here would be a worse case example. The service neutral is completely open, not connect somewhere between the neutral bus at the electrical panel and the source (utility transformer).
L1 to neutral bus loads and L2 to neutral bus loads are in series with one another.
Current is the same in all parts of a series circuit. Find I (current, amps)
L1 loads, 4 ohms total.
L2 loads, 6 ohms total.
R1 + R2 = Rt = 10 ohms
240V / 10 ohms = 24 amps
Find voltage drop across L1 to neutral bus loads.
E = I x R
24 amps x 4 ohms = 96 volts......
Find voltage drop across L2 to neutral bus loads.
24 amps x 6 ohms = 144 volts.....
The above example would be the extreme that could happen in the event of a total loss of a service neutral connection for the given loads.
A loose or corroded service neutral connection will have the same effect but because of resistance within the bad connection the voltage drop variables will change due to the amount of unbalanced load current placed upon it. And just to muddy the water the service
neutral to earth connection integrity becomes part of the equation as well. Most utility companies connect the neutral at the utility transformer to earth ground as well.
So basically in the case of a loose or corroded service neutral conductor where an unbalanced load is present at the electrical panel the Line with the bigger load will have a Line to neutral voltage lower than half the Line to Line voltage, and the other Line to neutral voltage higher than half of the Line to Line voltage. If the balanced load voltage is say 123V Line to neutral, (246V Line to Line), then one might easily see in an unbalanced load condition one side with a voltage of 115V and the other side 131V. And again it all depends how big the unbalanced load is and how loose/corroded the service neutral connection is.
Now you can see why incandescent bulbs could become brighter when the refrigerator kicks on.