Arrived and the customer had the thermostat off the wall and the gas valve set to pilot so it wouldn’t turn on. Found that once the thermostat got place back on the wall the furnace would start no matter that the temperature was set to. Tested the wires for any breaks and shirts which their were none. Replaced the thermostat and tested the system. No other issues to report. Charged the CC that was on file since it was under the $500 limit with the diagnostic charge.