That is a 3-way dimmer, so you'll have to replace it with a 3-way switch. The new 3-way switch will have 4 terminals (screws), 1 black (Common), 2 brass (Travelers), 1 green (Ground).
When working with 3-way switches, the
Common terminal will always be the odd color (odd man out). For example, on your current switch the Red wire is the Common. On a regular 3-way, the black (odd color) screw is the Common.
To prevent confusion, it's often a good idea to work with one wire at a time. Rather than disconnecting all the wires from the old switch, then trying to remember what went where.
- Start By turning off the power at the breaker, and verifying it's off with a non-contact voltage tester.
- Disconnect the bare copper wire from the old switch, and connect it to the green terminal on the new switch.
- Disconnect the black wire (the one connected to the red wire on the old switch), then connect it to the black (Common) terminal on the new switch.
- Disconnect the black and red travelers, and connect one to each brass terminal on the new switch.
- Turn the breaker on, and verify proper operation.
- Turn the breaker back off, and mount the switch in the box.
- Turn the breaker back on, and again verify proper operation.