I am diagnosing a heat pump. The customer said it worked great during the cooling season, but when she turned the thermostat to heating, the thermostat started smoking. I took off the cover to the thermostat, jumpered the red with yellow, ac worked great, then jumpered red with white, and started sparking alot so i couldnt keep it that way because i felt the transformer and it was getting very hot. Please help! Any ideas??