Honeywell T8400C Owner's Manual - Page 10

Troubleshooting Guide CAUTION To avoid possible equipment damage, do not operate cooling when outside temperature is below 50°F (10°C). See equipment manufacturer instructions. Heating or cooling does not come on. Temperature setting is too warm or cool. • Check that the SYSTEM switch on the thermostat is set to Heat or Cool. • Check the system fuse or circuit breaker and replace or reset if necessary. • Check for air movement at the register. • Check power to the heating or cooling equipment. • Adjust the temperature by pressing either the ▲ or ▼ key. 69-1490 10