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Air Conditioner is running constantly (it was shutting off after running for awhile and turning back on. Starts blowing strong cool air, then gets weaker after several hours. Discovered water dripping in vent by furnace and pooling on the floor.

I have a ceiling light at either end of my hallway, both controlled by a switch at each end. I had no trouble replacing the fixture at one end with a spotlight, as it just had a single cable with three wires. But when I went to replace the fixture at the other end, I discovered it has four cables going into it, totaling 12 wires. On one side of the fixture, three black wires are connected, and on the other side, one black and one red wire are hooked up. Additionally, three red wires are tucked into a connector but aren't attached to anything, and four ground wires aren't connected to the plastic fixture. Why are there so many wires here?? The main thing I need to know is how to identify which ones are live and which are neutral, or if it even matters how I connect them to the new fixture. I'm guessing the black and red wires together indicate they might be live, since a red one is involved. Any insights would be greatly appreciated. Thanks!

I'm trying to install an Ikea pendant light on my ceiling, but I'm having issues. There's a green and yellow ground wire coming from the ceiling, but the Ikea fixture only has spots for the blue and brown wires. The fixture is plastic. I've heard you can tape off the ground wire if it's not needed. Can someone tell me what type of tape I should use and what that actually involves? Or should I be using a wire connector instead? Can anyone advise on best course of action?! Many thanks