I have addded a new exhaust fan to an existing bathrrom with a vanity light. the power goes to the fixture then runs the wire back to the single switch. I ran the fan the same way running power from the bax to the fan then back to the switch (just like the light). when I hooked it up the breaker pops when I turn the fan off at the switch and will not let me reset the breaker unless the fan is set to on from the switch.....what am I doing wrong????please help!