Re-reading your question makes me worried....
Adding a source of voltage which will supply more current to a circuit that "isn't working", in case that fixes it, may just be adding enough power to melt things in a BAD circuit.
Maybe your current source of voltage is doing you a favor by "giving up".... NOT that this is a "safe" way to "test" things, unless you have a specially designed PSU that is "overload friendly", and even then is is only a bad idea, not a bad-idea-which-could-wreck-things. (Actually, things could still be wrecked, but not as many things.)
There are ways to figure out ahead of time what current SHOULD flow, and if your PSU is designed to be able to supply that much.