Returned to replaced burned defrost board. Located short in y wire that caused board failure. I was able to jump y over to another wire to correct short. While cycling the system, I found the system running cooling when no cooling call was made and should be running heat mode at the condenser. I tried the other available wires in the bundle with no success. We will need to return to pull a new low voltage wire from airhandler to the condenser (carrier system). Wire will need to go straight up the wall and through the soffit. Job will take 2 techs and 2 to 3 hours to complete. Office to make sure techs have a way to secure the wire to the wall with clips. System bypassed in cooling mode for now. Heat will not function until wire pulled. Home owner prepaid wire pull today.