If we are going to be able to help you the best we can, we really need a little more info. More specifically, what heli do you have, and what do you mean "did not work, but down in lower elevation"? What exactly did it do or not do, and how did the operation change at a lower elevation. Also, exactly how much experience do you have with helis? The more information you can provide about the problem, the more exact and helpful answers we can give. Hopefully we can get you sorted out and in the air so you can enjoy this hobby without any grief!