Genie GDO - operator runs, door not responding
I have a Genie GCG 350ML (chain glide, 0.5 HP, bought in 2004) opener that has been giving me a lot of trouble.
Currently, the opener makes a buzzing sound (can't call it a hum) when I hit the wall/remote button but the door does not move.
When I try to close the door using the opener, I expect the chain to move away from the opener and pass through the carriage. But the chain moves a couple of inches and stops. On pressing the wall control button again, the chain reverses direction. The door does not move at all.
When I try to open the door using the opener, the chain moves towards the opener but the door does not open. Once the chain reaches the open limit, it reverses direction.
I have replaced the worm and drive gears as well as the circuit board. I have checked to make sure that the door is balanced and I even got a repairman to take a look at the whole thing. Apart from urging me to replace the opener, he had no other solution to offer. I am able to open and close the door manually. I have also fiddled with the limit force switches and it has not changed anything.
Could this be a problem with the carriage mechanism? Genie's customer service (btw, very efficient) also does not have any suggestions. Have any of you seen this problem before? Can one of the experts please shed some light on what could be goinf on here?