Arrived on site to perform Diagnostic. Homeowner states that his thermostat is blank. We were just out recently and replaced the fan motor outside. Also came out to quote for a new system, but they are still not ready for that yet. Checked for power at the thermostat. Found that This is a battery operated thermostat. Replaced batteries, customer provided. Thermostat came on, cycled for cooling. Unit came on and started cooling. Checked electrical components. System is operational upon departure.