I have an existing light in a bathroom with 12/2 wire running to a switch. I have added a bathroom fan and another switch. On the bath fan I ran 14/2 wire from the switch to the fan. Having problems getting wired up correctly.

First what size circuit breaker is on this circuit. If it is a 20amp breaker you must use 12 gauge wire. If you have only one 12-2 cable in the switch box the power is being fed to the light. The power comes from the wiring in the light to the switch and goes back to the light itself when the switch is on. You must run a cable from the light to the fan to get the power there. You then run a cable from the fan to the switch. You connect the black of the power cable to the white of the switch leg and connect the black of the switch leg to the black of the fan itself.

Do you need a drawing?

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Thanks for your help!