I just took down a ceiling light fixture and now I'm stuck! I've got two black wires and two white wires, along with a couple of copper ground wires. I didn't take any photos of how the old fixture was wired, so I'm not sure which wire connects to what. I'm looking to install a new light and need some guidance on how to handle these unknown wires.
4 Answers
There are a few possibilities here. The wires could be going to another light, or one set might be for the switch. If it's a ceiling fan, they could also be set up so that the light and fan can be controlled independently. A lot of setups can get really complicated. Without knowing how the old fixture was wired, you'd need to figure out your specific setup to do it right.
If there's only one switch for the light, check the switch wiring. If both blacks are connected there with the whites tied together, then you can just connect like colors at the fixture. If it’s one black and one white on the switch, you'll have to do a bit of detective work with a multimeter to figure out which is which before connecting, so just keep safety as your priority here!
You might just be able to connect the wires by color, but honestly, I’d avoid that if you can. Ideally, you want to use a multimeter to test everything first. It’s much safer that way! If you’re not comfortable with that, I'd suggest reaching out to someone who knows what they’re doing
First things first, are the wires still all connected or have they been separated? Typically, one black wire is for the incoming power and the other might go to the next fixture. Same goes for the white wires. But if you're unsure and don’t have the equipment to test them, I’d recommend calling an electrician—it’s better to be safe!
Pigtailing like that is common for fixtures that are in series. Just a heads up, if this is for a ceiling fan, those often have separate wires for the fan and light. And trust me, if it's been altered by a previous owner, it can get pretty messy. Again, I'd still suggest getting a pro to check it out.

I appreciate the advice—definitely going to heed the warning!