Cannot program new remotes for Sears 139.651600
I searched the archives and didn't see a thread for this one, but forgive me if I ask a question that has already been covered.
I just moved into a rental house, and the garage door opener is a Sears (model in subject line). It looks like it's quite an older model. The one remote I was given works just fine, but it bulky and does not clip to a visor. I purchased two new Liftmaster (971LM) openers, which I cannot seem to program.
There is a red button on the back of the motor, and no indicator light. There is a sticker next to the button that says "wait 5 minutes and then reset". Is that the button I should be using to program the remotes? There are no other buttons, and I have tried several combinations of pressing button, holding down remote button - pressing button, pressing remote button twice - etc.
Thanks for your help!