Assuming there is a circuit breaker in the path between the battery and switch as MFL pointed out above, your direct wire from battery to switch is bypassing that breaker. If I had to guess, I would say that the circuit breaker is tripping as soon as it senses a load. I would start by replacing that breaker. And definitely put a fuse or CB in your temporary circuit as pointed out because it's possible that there's a short somewhere in or after the switch that could be causing the existing breaker to trip.
