Why does my heating or cooling system not respond, and what should I do?

First, press SYSTEM to ensure it's set to Heat (with temperature higher than inside temperature) or Cool (with temperature lower than inside temperature). Check that the circuit breaker is on, the power switch at your system is on, and the furnace door is closed. If 'Wait' is displayed, the compressor protection timer is active—wait 5 minutes for safe restart without damaging the compressor (page 15). These steps address the most common issues.