My heating or cooling system is not responding — what should I check?

First, ensure the System switch is set to the correct mode (Heat or Cool) and that the temperature is set higher than the inside temperature for heating, or lower for cooling. If the settings appear correct, wait 5 minutes for the system to respond, as the compressor protection feature may be active. (Page 10)

From the official Honeywell TH3000 Programmable Thermostat manual, page 10

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