Reciprocation Engine Induction And Cooling Systems Oral Practice Test

When coolant circulation to the heater core is poor, the heater can’t transfer enough heat to the cabin. The heater relies on hot coolant flowing through the heater core to warm the air that blows into the passenger compartment. If the flow is restricted, you’ll notice weaker heat, slower warming, or the cabin staying cooler than desired even with the heater set high. That directly describes reduced heater performance caused by insufficient heat transfer from the coolant loop. The other possibilities don’t fit the symptom as well. Pushing more heat from the heater would require more heat transfer, which isn’t possible with restricted flow. Engine overcooling could occur in some cooling-system faults, but it’s not the direct symptom of reduced heater performance. Higher fuel efficiency isn’t related to heater performance.