Craftsman 1/2 H/P Garage door starts down, then goes back up
I have a Craftsman Garage door opener, 1/2 HP chain drive. It's approx 4-5 years old.
The problem that I am having is it starts down, then after about a foot, it goes back up.
I have checked the photo eyes and they look fine, no blinking lights. Even if I hold the button down, the garage door returns up after a foot or so.
If I dis-connect the door from the chain, it still does the same thing.
Manually, I can raise and lower the door without any problems.
I get 5 blinking lights after the door returns back up.
I bought a used RPM sensor off of ebay ( I actually received 2). I tried both of those and still had the same problem.
I could buy a new sensor, but the person I bought the used sensor off, says they are good and he has 100% positive feedback, so I believe they are good.
Any other ideas? I am stuck. Any help would be appreciated.
Thanks in advance!