Ok I'm a new user to this site. I have an HD 73 door operator on one of my contracts that will not hold on the open position. As soon as it hits the DOL it lets go of the door and allows it to drift back closed about 6 to 9 inches then reopens. Any suggestions?

The weight of the linkage on those will pull the door closed along with the spirator tension. The operator has to be adjusted to mechanically lock open, the center of the sheave, the link arm pivot on the sheave and the drive arm pivot should be in a straight line when on the open limit. It could even be adjusted just a hair past if they really want to close as long as the mechanical stop is set so the door can't over rotate.

That was the original problem was that the short arm was reversing itself. It was over rotating. I adjusted the mechanical stops on the sheave to align the arms, but then I still have the problem of it not locking or holding in the fully open position. I am working on getting everything together to mod to a GAL MOVFR2. They have a much more user friendly product and it's a galaxy controller anyway.
Never had this problem with the HD73 before.