Carrier hvac fan wont stop running
 

I replaced my thermostat and got the wires mixed up. Now the fan won't turn off... do i need to replace the transformer?

Reinstall the old thermostat and check if something has damaged.

The fan probably won't turn off because your thermostat has the fan set to on instead of auto...

Its not the transformer. Check to made sure that the g terminal wire and the R terminal wires arent touching. Sounds like you have the wires mixed up. The best way to resolve this issue is to open up your furnace or air handler and see what color wires are connected to the terminals in the AHU.

also check your low voltage fuse on the control board.