Have HVAC Questions? Ask an HVAC Expert for Answers
Did you turn power off to indoor before you started? And tell me what wires you had to what terminals on old and where you put them on new?
If either of the following conditions exist you possibly blew a small 3 or 5 amp auto type fuse in the indoor unit.
1.If you had a C wire on old thermostat and did not turn off power to indoor unit, it could have touched the R wire and blew fuse.
2.If you had a blue wire to C and you connected it to O/B terminal, this also would blow fuse.
If either of these is so, look in the indoor unit for a small 3 or 5 amp fuse on control board.If it is blown replace it .If you had a blue C wire, remove it and tape it off.
WE can go from here. Do not rate answer until we are finished.