If your thermostat is blinking "heat on," it typically indicates that the thermostat is in a delay mode or a safety feature has been activated. Here are some possible reasons: Delay mode: Many thermostats have a built-in delay feature to protect your HVAC system from short-cycling, which can cause damage and reduce efficiency. The delay mode prevents the system from turning on and off too quickly. During this delay period, the thermostat may blink "heat on" to indicate that it's waiting to activate the heating system. The delay usually lasts for a few minutes, after which the thermostat should stop blinking and start heating your home. Safety feature activation: Some thermostats have safety features that will cause the "heat on" to blink if the system detects a potential issue, such as a dirty air filter, a malfunctioning component, or an overheating furnace. This is to alert you to the problem and protect your HVAC system from damage. Check your air filter and replace or clean it if necessary. If the issue persists, contact Martino HVAC to inspect your system and diagnose the problem. Communication error: In some cases, the blinking "heat on" might indicate a communication error between the thermostat and your HVAC system. Ensure that your thermostat is correctly wired and configured for your system. If you're unsure about the wiring or configuration, contact Martino HVAC for assistance. If your thermostat continues to blink "heat on" and you cannot identify the cause, it's essential to contact Martino HVAC for a professional assessment and any necessary repairs. Our technicians can diagnose the issue and help restore proper function to your thermostat and heating system.