In my previous response to the post about FindRoot, I left out a modifier ("typically") that makes for an inaccurate statement. That last paragraph should have read:
> FindRoot is typically used for searching for a numerical solution to a single > equation. It uses a variant of Newton's method and hence requires some > initial guesses to get it started. It will use a secant method > if you provide two initial guesses.
The reason that I suggested other methods is that there is great difficulty finding solutions for large systems with Newton's method if you don't really know where to start; that is, if you cannot start with decent initial guesses. If you are just taking wild guesses for the initial values for such a system (16 unknowns in your case), you will almost certainly fail.