Have you tried adjusting the set screws on the photo sensors? Or checked what colors the leds are showing to verify the sensor works and is detecting things? You are using the 42EF-D1NAK-A2 ClearSight RightSight correct? I looked up the part on rockwell's website and found installation instructions. Click on the 'library' link and search for something like '42EF'. It mentions calibrating the sensor and describes what the led colors mean. If the leds are working then you know you have the sensor calibrated right and should get output on the signal line.
I also remember getting a data sheet with the sensors last year tho I could not find it on Rockwell's site. Try searching the forums, I found lots of hits from last year, like this one for example:
http://www.chiefdelphi.com/forums/sh...=photo+sensors