I have a switch in my master bedroom that my family replaced. The controls are switched. The fan turns on when you put the light switch on and the light turns on only when the fan switch is all the way up. The scary part is when I turn one of the switches on I can see a blue spark inside the switch. The picture attached is what the switch looks like. Please Help!
There may be a problem depending on the model you have the s2-lf-wh model 300w on the dimmer it was not clear if they used a different type of control on the 2 sides it just stated 300w 2.5amps. The other models s2-lfsq-wh show single pole 300w for the fan and 150w for the light on this model it may damage the electronics if hooked up backwards. With most electronic controllers a flash can be a bad thing so I would want to correct the issue just in case so your nice new switch keeps working for years.
This switch will have one screw or a wire on the back for the fan and one for the light. These two have simply been connected to the opposite wires in the wall. They are most likely labeled on the back of the switch, but a safe bet would be that the side the wire or screw is on matches the slider on the front. For a non-electrical fix, just put a new label on the front.
The blue spark probably isn't a concern. The large slit on the front of the switch makes the spark more apparent, but when an electrical contact closes, sparks can happen.