We have an old genie model SP99 garage door opener. The motor stills works, the plastic gear still turns but the door will not open or close without assistance. Could the chain sprocket 'slip' when the gear is turning? When giving assistance the chain does move down the track like normal to it's limits and then stops like it should. I see that a gear wheel and sprocket assembly is available as a replacement part (#26289). Do you think the problem with my opener is a bad gear and sprocket assembly? When I stand on a ladder and watch the plastic gear wheel, it does spin without any difficulty when switched on, but the chain does not move. If the gear and sprocket assembly is bad, is this a difficult replacement job for a do-it-yourselfer?

Could you further explain what you mean "it does spin without any difficulty when switched on, but the chain does not move" Is the gear turning on the chain but the chain stands still? That can only happen when the teeth are worn off the gear. Replacement isn't terribly difficult but installing a new opener for $140 isn't any more difficult. Its been my experinec that when an opener starts to fail many parts are getting ready to follow suit. Its you call if you are feeling handy but If you hired me I'd try to talk you into a new unit and be done with it.

Thank you for your quick assistance. I got back up on the ladder to get a better look and I took off the plate that covers and protects the chain sprocket and large plastic gear This cover plate has a bushing that keeps the chain sprocket/large plastic gear assembly in place. What you thought was happening appears to be true. The teeth on the round plastic gear are not coming into good contact with the drive gear shaft coming from the motor. Looking at the setup as it operates now, I think this might just be a secondary reason why I am experiencing problems. The chain sprocket has no teeth to hook on to the chain. The large round plastic gear and the sprocket both turn when they engage with the drive gear while power is on, but without any teeth the chain sprocket is having trouble gripping the chain. I think because the sprocket teeth are worn down to nubs at best, this is allowing too much 'play' in the alignment of the large plastic gear wheel and the drive gear resulting in a gap between the drive gear and the round plastic gear. Am I correct in my thinking that the chain sprocket should have teeth to mesh with the chain? If I went with the cheaper option of making a repair by replacing the round plastic gear and chain sprocket assembly rather than replacing the entire garage door opener unit, could you tell me if I can just pull the old gear assembly off and pop a replacement assembly back on, or is it much more than that?

No, I think you have described a fairly simple repair. You should plan to disconnect the opener from the ceiling and lower the motor and arm to a saw horse so you can be a better look at that gear. Remove the chain by loosening the tensioner and then open the master link in the cahin. Once the cahin is off the gear is likely held on a shaft with a single clip. Before you do these steps be sure you have the new part in hand. Good luck, Bob

I HAVE AN GARAGE DOOR OPENER AND I NEED PART (Genie Garage Door Opener Gear & Sprocket - Part # 26289R) THE GARAGE DOOR MODEL NUMBER IS 810.