I have a 12-year old 1/2-hp Craftsman garage door opener that will only close without holding down the wall switch on rare ocassions. As the temperature has dropped, successful closings have decreased. Every indication is that the problem is with the eye sensor, however the last time I pulled the receiver sensor completely out of alignment, and the door worked fine with the remote (doesn't anymore). The light will not go on on the receiver even when aligned, but there is .5 v reaching the sensor.

Is it likely the sensor is bad, and is it worth replacing or should I replace the whole unit? Everything seems to work fine otherwise. I gather from reading other postings that bypassing the sensor is not an option.