I arrived for a non member no heat call. I first inspected the furnace and found the low voltage fuse and main control board to have been burnt and non operational. I made the homeowner aware of the issue with the system and suggested to replace the furnace bs repair. The homeowners decided to repair the system and not to replace the furnace. I picked up the control board and installed a new fuse. I cycled the system on and the furnace ran for able 5 min and the fuse blew. I replace the fuse and traced down a shot in the common wire in the thermostats wire that runs to the control and thermostat. I recommend to replace the thermostat wire at this time. The homeowners wanted to try and repair the wire there self. I instructed to unplug the power to the furnace before messing with the thermostat wire. If the fuse or control board goes out because of the short this will not be covered under warranty as to this is the reason the fuse and control board failed. I cleaned up the wiring as muc