Gaarage Door I'm opening the garage door manually. I disconnected the trolley to do this. When I lift up the garage door is there something to keep the garage door up. After I remove my hand off the handle the door just rolls back down. I dont know what type of mechanism is used to keep the door up. The door works fine using the remote mode.

issue with counterbalance springs. when you release trolley, door should balance at half way open. if i rises all the way on its own, or falls closed, then the springs are an issue and motor and trolley are working very hard in one direction or the other.

You have to make sure the trolley on the drive engages with the catch on the door. You may have to lift the door to the point it will engage while you are running the trolley in the close mode. Check that the trolley latch is open and ready to engage the catch. There is usually a rope to pull on to do this.

Turn the up force adjustment on the back of the opener up a little higher.

The torsion springs might need adjustment.

Pull emergency release, and manually lift door to half-open position.

When you release the door, it should stay in place.
If it almost "slams" down, the springs are not doing their job to "balance" the weight of the door itself.
The opener isn't designed to overcome the weight of the unsupported (no spring assist) door.

Over time, the springs take a "set", and might need a readjustment
THIS IS A JOB FOR PROFESSIONALS!!!
The springs are under tremendous pressure loading, and can even kill someone if they do not know what they are doing!

Is the door stuck in the open position? If so the trolley is probably jammed against the bolt just in front of the motor unit. Loosen the chain enough to free the trolley and then run the opener until the door is closed. While the door is closed locate the 'up limit' on the side of the motor unit and turn this control 2 complete turns in the opposite direction of the arrow printed on the cover. Tighten the chain.

You can adjust the length of the arm between the trolley and door so that it is in a vertical position when the door is closed. This will prevent your problem.

It sure sounds like you have a broken door spring. While you are at it remove the cover and take a good look at the drive gear. It is white nylon and is just in front of the motor. Might be stripped and unable to take the weight of the door.

If the door operates freely without any binding, while operating it manually then It would appear that the obstruction sensor mounted across the doors path is ether out of alignment, lens dirty,or malfunctioning

It sounds like that missing pin is your problem, the trolley attached to the arm with the pin. Its hard to diagnose, but call in a Door Opener guy and he can probably fix it in a few seconds for free. Otherwise, try and find the pin or something like it to fix the arm in place and see if you can MANUALLY operate the door that way. BTW, Disconnect from power before you try and experiment.

two problems. why aren't inner and outter trolley connecting. did you leave rope is disconnect position. Second problem is door springs do not seem balanced. you should be able to lift door halve way up and let go. it should pretty much stay there; go up or down slowly ok. fly up or crash down; need to adjust springs/cables or maybe wrong springs.