System analysis x1 Furnace has power and runs when thermostat is bypassed. Checked thermostat batteries and batteries corroded and acid fell onto control board causing it to fail. Since issue was quick to find I did a visual inspection of the whole unit and found organic growth in the supply plenum. Recommended replacing thermostat with Honeywell pro 8000 and adding IAQ package. All recommendations were accepted, replaced thermostat and Will need to come back tomorrow to add the IAQ package (non ozone air scrubber and sanuvox coil treatment). Made sure system was fully operational before leaving for both heating and cooling.