Service diagnostic found that when set to cool the system would run in heating mode. There was no 24v signal coming out to the condenser on the O wire to switch the reversing valve to cooling. I traced back the wiring and found a splice with wire nuts in the attic near the exterior wall where the wires penetrate out of the home and run down to the condenser. That splice was the last place I was getting a call on the O wire. I looked over the system and also found that the condensation drain line was clogged. Options for repair were presented to the homeowners. They chose to have the drain line cleared and to have the wiring repaired. I ran fresh wire from the condenser up into the attic and cut back to wires to make a clean connection. As I pulled back the sheath on the wires to remake the connection, I found that the wire had several spots where the insulation between the wires had rubbed away. I wired in the new wire to test the system. The system is now running in co