My house is 100 years old. Two bulbs (one on the first and one on the second floor) are controlled by two switches (one on the first floor and one on the second). I checked the both switches. They are good, but don't have power. Surprisingly, the lights can be on once or twice a year. The wiring is original. Thank you for your help.
Electrical problems such as this, you're more than likely going to need an electrician..I will NEVER advise people to dig into wiring.
A bad sign:
You mentioned this circuit only works a couple times a year ? Oh boy, that is NOT good.
What it could be, and what a homeowner can do without digging into the wiring:
Post a person AT EACH SWITCH for ease of troubleshooting. (person 1, person 2) Person 1: Flip the switch, (only once) & observe the light What happens ? Does the light come on ? If yes or no Person 2: Flip the switch ( only once) & observe the light What happens ? Does the light come on or turn off ?
Now that both switches are in the opposite positions of where you had them:
Person 1: Flip the switch... What happens ? If the light comes on or doesn't come on: Flip it again. Once again, if the light comes or doesn't come on... Person 2: Flip the switch... What happens Wether the lights come on or not, Flip the switch again.
All the above is doing is checking to see if one or more of the switches are bad or if they were possibly MISWIRED.
If you ever remember these working fine at one time, I can say with a good degree of certainty that it's a faulty switch or switches. And if it's only one that's bad, I'd still replace both due to age alone.
It's always best to get a electrician involved when you see all your breakers are on and you've got a intermittent problem.
If your house is 100 years old and the wiring is the original - you will not have power at the switches - You will have a switched NEUTRAL. This is not allowed anymore in the Electrical code for an obvious reason. Lets Discuss:
1: Your bulb sockets are always hot (100 years ago this was common - and no I am not that old ..). This means you can get electrocuted when installing light bulbs - touching ground and the bulb base - will give you plenty to think about - or maybe help someone inherit early.
Your neutrals are switched through the switches. Your Bulbs are wired hot.
I don't know what you mean by this: "Surprisingly, the lights can be on once or twice a year."
JUST an FYI: You might want to consider having your whole house rewired to current code standards - it will be much safer for you and your family.