The first and most important issue is a fuse should have blown which would protect the wiring in this type of failure.
A test of the switch can be done with an ohmmeter. With the wires disconnected, test each of the two terminals with respect to ground. You should have no resistance reading on either terminal.
Also a short to ground could be occurring somewhere else in the circuit. But it seems like the switch is the problem.
The 42 amp rating is the capacity of the switch contacts to handle current up to 42 amps without damage. Not an issue in this situation.