okay my apt building was built in 1975 I am changing my light fixture new from home depot and the ground wire, the black and white wire are basic on the new fixture. I am looking in the case box in my ceiling all I see is a black wire attached to red, and a yellow wire attached to a white wire which then attaches to another two white wires (then gos go's up behind the casing) I am not sure which is the ground here. There is a copper looking wire that is thick, thick it just isnt as malleable as the new ground wire that is on my new light fixture. It seems very difficult to maneuver.. Could this be my ground from the ceiling. It was attached to the mount of the old fixture my a screw.
All wiring is different but the basics remain the same. Before attempting anything please turn off the power. If I have the good picture in my head, there are extension wires added to the black and white this would be done if the wire run though the wall was too short and needed a little extra to get wired properly to a fixture. If I look at the bad picture in my head you have a jump cable attached which is running to a second outlet or light fixture. If the extra wires go back into the ceiling leading somewhere else then it is probably running to a different fixture and this isn't the best way to run electrical. It could potentially overload your circuit. If it has been working for 40 years without a problem you are probably ok, so long as the fixture you're adding is within the same category as the fixture you're removing. The thick copper wire will be your ground wire and should be attached to the box, and to the outlet itself with screws. Good luck with that fixture.
The wire that was attached to the mount is your ground. (It should be thicker than the one from the fixture. - Use a 'wirenut' to make the connection.) The White wires will be your 'Neutrals'- 'White' from your new fixture. For the 'Black' from the fixture, use the same wire that was connected to the old fixtures 'black'. If you didn't keep track of which is which, then you are now 'in over your head'. Get experienced help before you cause damage or hurt yourself.
