My home is 50 years old and uses a fuse box. I have a stairway that uses two three way switches to control one light. They were starting to fail so I purchased two replacement switches. When I removed the old witches I did not see any labeling as to common so I disconnected all wires from both switches. My first attempt to wire blew the fuse and same with second attempt.
After doing some research on wiring three way switches and troubleshooting, I did some testing. Using a volt meter I connected one lead to a ground and used the other lead to find the hot. Here is what I found:
Outlet box A
Black wire 120v
Red wire 51v
White wire 0v

Outlet box B
Black wire 120v
Red wire 51v
White wire 0v

Can anyone help me to make sense out of this? It is my understanding that I should only find one hot wire out of the two sets of three wires and I have no idea how I am getting 51v AC from the red wires.