I installed a new ceiling fan in our living room that came with a remote. Per the fan instructions all of the wires were connected properly but I had a left over red wire from the old fan. I capped it off properly. On the wall plate the old fan had a separate switch to turn the light on/off and then a rotary dial switch to control the fan on/off and speed. I ended up not using the rotary dial switch and have everything connected to other switch and leave it on so the remote will work. All good with one exception…
After all this my porch lights, which are tied to a dawn/dusk sensor, quit working (the sensor). The lights will come on when the switch is flipped on but no sensor operation. I climbed up and opened up the photocell and low and behold there is a common red wire in there; then I went to the breaker box and discovered my living room ceiling fan and the front porch lights are on the same breaker. Since I capped off the red wire from the box up where the new ceiling fan is mounted I'm assuming that is causing my problem with the porch sensor? Where do I connect the red wire I capped off at the ceiling fan, thank you. 
Best Answer
Before you do anything else try resetting the wall switch for the porch light. When you turned off power to the fan (and the porch light) it probably affected the sensor setting. Check your instructions for resetting the sensor from your installation pamphlet or on-line.
The red wire in the fan is probably only part of the switch loop you're not using any longer.