adjusting older Sears garage door operator
Hi. It looks like there are a few experts here. Can I get some help? Here's the story. I had an older Sears operator, model 139.53210, a 1/3 HP model. It is "old school" no sensors; just opens & closes the door. I had a bad spring on the door, and it put a strain on the operator, and chewed up the plastic gear. Fortuantly, I had a similar operator as a spare. It is a similar vintage Sears. It looks identical to the old one, with two differences. First, its 1/2 HP with model 13953600, and the remote has 9 switches instead of 7. So, anyway, I fixed the spring so the door is balanced now, and removed the old operator & installed the "new" one. My problem now is limits. The door only came about half-way up & stopped. Instead of using the limit adjustment screws, beacuse it was so far off, I did it "old school" by disconnecting the chain & moving the door up & reconnecting. This solved the "up" problem. But I'm having a "down" problem, which was already happening before I moved the drive chain. What happens is this: The door travels all the way to the "closed" position and stops. Then about 2 seconds later, it starts to travel back up. At first I thought it was the force adjustment being too sensitive & triggering the auto-reverse. So I adjusted the force control, and that's not it. Any ideas on this? maybe it's the sensitivity of the auto-reverse? But I don't see a way to adjust that. Remember, this is an old model; no sensor reflectors. Also, is there a way for me to use my old 7 dip switch remote control with the 9 switch operator? Thanks to all.