The unit in the wall has three wires. Two black and one green. I removed a dimmer from the wall and wired in this switch. Green to ground, black to black and the other black to white. The instruction then say to turn on the power at the circuit breaker and hold the on/off button for 3 seconds or until the red light blinks two times. No such luck. I reversed the black wire connections and still the same. There is no voltage at the fan no matter how I push buttons on the wall unit. The works fine with the old switch in place. Any ideas would be well appreciated. Paul

Sounds like a bad switch, double check that you have followed the directions for wiring exactly. Sometimes dimmers use weird color codes that may not match your home's wiring.

So are you saying the switch itself had wires on it, one whire and one black? " black to black and the other black to white"