Where are the code numbers
by owner
where is the code numbers on the unit?
Go to
http://www.garagedooropenerguide.com/installationmanuals.html to find your online manual for illustrations of the unit.
You don't mention which brand yours is, but if you have Overhead Door, the only manuals online are listed as Genie, which makes both brands.
Then there are a lot of store brands made by Liftmaster as well as by Genie.