Why must you ensure the engine is full of coolant before turning on power to a heater?

Ensuring that the engine is full of coolant before turning on power to a heater is crucial because the heater relies on the proper circulation of coolant to function effectively. When the heater is activated without sufficient coolant, it can lead to overheating. The heating element may not cool down properly if there is not enough fluid to absorb and dissipate the heat being generated, which can ultimately cause the heating components to burn out or fail. Protecting the integrity of the heater and ensuring it operates efficiently depends on having adequate coolant levels, which prevents damage and maintains the overall functionality of the heating system.