A3 central locking pump, bought used one,doesnt work on my car, any idea what i need to do to make it work?

My part number is 8L0 862 257 P the used pump I purchased is the same but ends in 'H' and ideas why it wont work on my car? Do you know how to make it work?|||my answer is try to check it out first on auto repair shop...,|||i believe it is a vacuum type pump. Maybe the old one was ok, but you have a split or punctured air hose? Check all of those first.?|||Maybe it wasn't built for your car?!?! Get one that was built for your car model.