The answer to 'why is my junction box dimming lights' is that there are a few common causes, including loose connections, overloading the circuit, and issues with the light fixtures or bulbs. Dimming or flickering lights can be a sign of an electrical problem that needs to be addressed.
First, check the connections in the junction box. Loose wires or terminals can cause resistance and voltage drops, leading to dimming lights. Tighten any loose connections and ensure the wires are secure. Another potential cause is overloading the circuit - if you've added too many lights or high-wattage bulbs, the circuit may be overwhelmed. Try reducing the load by using lower-wattage bulbs or removing some fixtures. Finally, the issue could be with the light fixtures or bulbs themselves. Faulty or old components can cause dimming, so inspect the lights and replace as needed.