Cousin of mine has an Overhead Door garage door opener. It's the Python 2 (model CG800ML). I'm trying to diagnose some problems and Overhead door, in their infinite wisdom (and infinite desire to force you to call them for service) does not have the owners manual published electronically. Therefore I am forced to rely on you bunch of clowns for advice.
1. The door will not stay in a given position. If you stop it in any position, the weight of the door causes it to slowly creep closed. On occasion it will decide to actually lock in position, but not every time and not very often.
2. Starting from a completely open state, the door will begin to close but will reverse about 1/10th the way down. Changing the closing force setting does nothing.
3. Starting from a completely closed state, the door will beging to open but will reverse about 1/10th the way up. Changing the open force setting does nothing.
4. Starting from any location, the door will move about 1/10 of it's travel before reversing up/down (doesn't matter if you're opening or closing).
5. The electric eyes are "seeing" each other as both lights (one red, one green) are on and unblinking. Interrupting the beam causes the red light to blink. I have cleaned the lenses just in case. I have also swapped sides with the sensors, again just in case. No change either way.
The unit is all plastic internally. Even the gearbox is completely plastic-cased and the motor mounts are small plastic tabs. It's about the cheapest looking and feeling thing I've seen in a long time. There are only three parts in the case - motor, gear assembly, and system board (all the controls and electronics, even the adjustment pots, are integrated into the same board). Any one of these items would cost almost as much as buying a new unit. For that reason I hesitate to put more than a few minutes into diagnosis but wanted to make sure I wasn't overlooking something simple.