Hi. I've had a 1/2 HP model 139.53629SRT for 11 years. It has always worked fine. By hand it will open now too. But this morning it stopped working automatically. It will raise about 3" and stop. Pressing the button causes it to close again. I can't see it bound on anything, and as I say, it opens manually.

I don't have a manual to trouble shoot this. Does anyone have a link to a manual online? Barring that, does anyone have troubleshooting suggestion?

Many thanks.