Tech found display of thermostat was blank customer informed she would take cover off and some wires were showing tech took pictures tech found power to thermostat 28v from system. Tech informed home owner of findings and would need to replace thermostat to further diagnosis. Homeowner approved tech installed new thermostat and once a cooling call found low voltage fuse to blow. Tech inspected system found fuse was newer then the system ternate informed tech that the other company had replaced some things in there tech suspects they found a blown fuse replaced it then found no display at thermostat. Tech found a short in the blower wire harness rubbing to the blowerhousing. Tech repaired fuse and tested system system is operating properly at this time tech informed ternate on operation of thermostat cycled system on heat gas heat and cool all are operating properly at this time. Tech collected via phone.