Yes, to let someone down means you disappointed them.
I´d like to ask you this, considering you are a native.
If I want to say that something won´t be a disappointment, is it good to say: "It won´t let down" ?
Or necessarily I have to add "me" to the sentence and say "It won´t let ME down" (adding "me" to the sentence)? can I take "me" off ?
In spanish, I can take "me" off and say: No decepcionará.
Thanks in advance.
Thanks for your help. I was looking for an answer to my question and I found an article of a Boston newspaper in the web and its title was "Michigan won't let down". This article is old and talks about a match of the Michigan football team. Can I translate it like this "Michigan no decepcionara (o fallara)" ?
I agree, after seeing the same (truncated) link. Boston College is a weaker team, but Michigan will not be over-confident, it will play its best game.When it says that the Michigan team won't "let down," it means they won't relax even though they're facing a much weaker team. More usual ways of saying this would be "won't let up" or "won't let their guard down."