You need access you something when you need to assess it. For example, if you need to assess the locker of a rich man, you need to access it. Access is a way of approach, a method or reaching or entry.
Assess is to set an estimated value on property, etc. for taxation; estimate, appraise: “Income tax officials asses the properties of rich men.”
Excess, on the other hand, means when something surpasses a limit or is surplus. For example: The excess liquor he had at the party meant that he had a bad hangover the next day.