Most combination locks can be 'felt' to click when the tumblers are inline. Move each set gently and you should be able to feel as each one moves to the opening position. It may take some trial and error but if you are patient it should work.
You state that it is already open. Doesn't that mean it's already "unlocked"?
look it up on youtube how to reset a padlock
is that a car or transportation question?
i found it at the back of my toolbox, it is open i have forgotten the conbination
