Thanks creek side. It wasn't the door as I could open and close it easily with one hand with no binding. I took down the motor unit and brought it inside to my work bench, tore it apart screw by screw and connector by connector, and gave it a good cleaning. Put it back together and hooked everything up - works perfectly now! I think it must have been oxidation on some of the internal connectors, or it could just be that taking everything down loosened up something that may have been binding a little on the screw drive. Now I'll just have to wait to see how it works in the summer...

The garage door opener "can't" close by itself. It can reopen itself if the "photocells" are even "slightly" out of alignment. The only way the door can open,(at 2:00 the bars get out??? someone is fooling around??) is if someone has a programmed remote control to your door, or there is a slight short in the wire from the doorbell (wall) button end or the end of the wall button that connects to the back of the door opener. I have seen this. Sometimes they use speaker type wire that has several strands of wire. They may have frayed just slight. If just one strand of frayed wire is just barely touching the other contact. It will activate the door opener. Just a person walking above the door opener can activate the door without knowing. Most of the time they use a single strand wire and this does not usually happen. Lets try this first...Clear your board of all frequencies,(by holding in the programming button on the back of the board, it will be a colored button). Re program your exisiting remote controls and keypad back into the board. Check the wire behind the wall control, check the connection where the wires connect to the back of the opener. Make sure they are connected and are tight and not touching other contacts. There are many reasons for the door to "reverse". The door should "never" close without a command from a remote or wall control.. Dan

Try increasing the 'down force'. This is a control on the rear of the motor unit near where all those white wires go.

I figured it out. Problem with adjusting the limit switches was due to a missing pin on a gear that is on the main motor shaft that turns another gear that moves a plastic screw that hits the up and down limit switches. In other words, the internal up/down limit switches were not getting consistant feedback of the garage door position. Nothing that a twisty tie from a garbage bag couldn't fix. So that problem was fixed. The garage door now moves and it now moves up and down without whacking the header going down and the stop limit bolt (protecting the GDO motor unit) on the way up. I knew I was wasting time when the manual says a single rotation on either screw would result in a 2 inch travel change. and nothing I did was consistant. It either hit the bolt or header or it would just HUM and not do anything. I think the original problem of why the belt's tention spring/bolt came undone was due to excessive vibration due to non-sufficient belt tension. As soon as i got the garage door operational, I noticed it was hecka jerky initially going up or initially going down. Mid-travel was smoother. By tightening the nut (collapsing the tension spring) to the 1.25 inches specified in the owners manual seemed to make the garage door much smoother. When I have the time, I'll adjust the force screws down. I think I have them maxxed out right now. I'll also test the safety/reversing feature. For now, it open and closes smoothly. I'm happy. So, while the owners manual didn't tell me to open the thing up, common sense told me to. Also, this unit has a diagnostic feature. When you press the LEARN button, it will light up the diagnostic light and blink. 5 blinks told me the motor was overheated or the RPM sensor wasn't happy. No mention of what the RPM sensor was. I'm assuming something was stuck. Anyways, adjusting the limit switches got it moving and once I cracked open the motor housing case and saw the limit switches in action and saw how misaligned they were, it was a pretty easy fix. Glad I disconnected the door so I could cycle the belt for testing without crashing the door. that made way too much noise at 10PM tonight. Once again, thanks for your help and I hope something in this helps someone.