Diagnostic/ Both systems heating in cool mode. Arrived and wired R to O on the right side condenser to get it cooling so I could examine the left side system. I found that I had no voltage at O in the condenser and Y was cutting out sometimes too. I inspected the low voltage wiring and found a junction where all wires took orange wire nuts instead of blue ones. I installed blue wire nuts (smaller and tighter) and checked the system. It began cooling properly. I did the same thing on the right side system but still got no signal on the O wire. I replaced the T6 thermostat with a new one and tested the system. Both systems are now cooling properly and the T6 thermostat comes with a 1-year warranty. Thank you for your business. Havana FL