I decided to be handy and change all of my receptacles in the house. Everything went well until the garage. There are 3 light switches in the garage that go to 1 light source that has me stumped. Two light switches are 3-ways and one is a 4-way switch. I messed something up because the 4-way has to be in the on position in order for the 2 other switches to work. The 4-way has 2 black and 2 purple wires, while the 3-ways are all black because it is 1950"s wiring. Thoughts?
Just to clarify, the travelers on a 4 way are connected to the top terminals from one three way and the bottom terminals from the other.
NOT from side to side.
Google 4 way switch and check the wiring diagrams against what you have done. Like here.
A 4 way just switches the travelers from a 3 way, if one leg is wrong on the 4 way or one of the 3 ways is wrong, not working in all the positions is common. To help figure out where the problem is a list to all 3 switches in each position will be needed.