Many times when you work on an automobile or electronic product you come across plastic wire connectors. Unfortunately, there are thousands of different connectors, from butt connectors to press-on connectors to individual proprietary connectors used for just one application. However, ultimately you can remove a wire from any plastic connector.
Inspect the plastic connector for a locking mechanism. In most cases, the lock is a "tab" lock that presses over a ridge moulded into the plastic housing. If you locate one, pry up on the plastic tab with a pair of pliers to open the housing. Once open, pull the wire out of the connector.
Grip the wire with your thumb and forefinger where the wire goes into the connector. Hold the connector with your other hand and attempt to pull the wire out of the connector. In most cases, connectors either hold the wire in with a small metal prong or they are crushed onto the wire. With a gentle tug, the wire usually pulls out of the connector.
Place a pair of wire cutters next to the connector and cut the wire to remove it from the connector. Make sure you cut as close to the connector as possible so you have enough wire to create a splice if necessary to reconnect the wire.
Make sure to shut off the power before working on any household fixture or wire.