When the engine is not running, which mode is the blend door in?

When the engine is not running, which mode is the blend door in?

• A. The blend door is in the 'hot air mode.'
• B. The blend door is in the 'cold air mode.'
• C. The blend door is closed.
• D. The blend door is in the 'auto' mode.

Answer: (B)

When the engine isn’t running, the heater core isn’t heated because there’s no circulating hot coolant. The blend door’s job is to mix air that goes through the heater core with air that bypasses it. Since there’s no heat source available, the system defaults to sending air without passing through the heater core—that’s the cold air path. The other modes would require heat being produced, or active control powered, which isn’t available when the engine is off. So the blend door ends up in cold air mode.

When the engine isn’t running, the heater core isn’t heated because there’s no circulating hot coolant. The blend door’s job is to mix air that goes through the heater core with air that bypasses it. Since there’s no heat source available, the system defaults to sending air without passing through the heater core—that’s the cold air path. The other modes would require heat being produced, or active control powered, which isn’t available when the engine is off. So the blend door ends up in cold air mode.