Today at one of my service calls, the customer stated that the AC wasn't working properly. When I went in attic, the furnace was operating while in cool mode. This is a duel fuel system with gas as the primary heat and the heat pump for emergency heat. I took off the wires at the control board and jumped R and Y and O and the furnace did not come on.I took wires off at the thermostat and I jumped R,Y,O furnace did not come on, I jumped R,Y and the furnace did not come on. I went outside to see if I was getting 24v to outside unit while t-stat was in cool mode. I was getting 24v from Y to common but outside unit wasnt coming on. The pressure switch had been cut and wire nutted together. I then jumped y( t-stat wire) straight to contactor and the outside unit came on in cool mode and in heat pump mode . So apparently I have a bad defrost board. However, the gas furnace still continued to run. I don't think its the board because I took W off of the board and the outside unit ran and the furnace didn't come on.I cannot figure out why the furnace runs while in cool mode or EM heat mode. My co-workers think its the thermostat or a short somewhere in the t-stat wire. I'm not totally convinced its the thermostat. I'm missing something. Any advice or troubleshooting tip would be helpful! Thanks