It would be nice if he could save his flashlightis to try using baking soda mixed with a bit of warm water, mixed so that it's a bit looser than a paste, but not watery.
This mixture is VERY good at neutralizing battery corrosion, then follow up with the alcohol cleaning again. I've saved many of my friend's Maglites that had batteries so corroded that we had to drill them out first.
Yes, the switch is ok. Honestly, I did see that coming. The flashlight was weaking, until die. Probably, the leaks was damaging the circuit.Did you try eliminating the switch as the bad component? There is a thread on troubleshooting which can help you in your diagnosis.