Yesterday I came home and found that my indoor unit burn the transformer. I installed a replacement but the A/C wouldn't work. After a few minutes I noticed a burn smell coming from the unit, I immediately unplug the unit. Today I went ahead and tested the transformer with everything off. It was giving around 26 volts. I went ahead and fused the secondary side with a 1.5 amp fuse. When turning on the fan alone it works fine. When positioning the thermostat in heat or cool, I blew up the fuse right away. I took off the fuse and repeated the process using the door switch so I could get the power off in a hurry, I get a small buzz sound from the transformer and the voltage reading drops to around 8 to 9 volts. At the same time the transformer starts getting hot. I check the outside unit (heat pump) contactor winding and is not open. Any suggestion will be appreciated. I also bougth a new transformer but not using it since the first one tested good without major load on it.