ASE G1 Auto Maintenance and Light RepairMaintenance and Light RepairMedium
A client complains that their vehicle's cabin heater is blowing cold air, even after the engine has reached operating temperature. Which of the following is the MOST likely cause?
- AA low engine oil level.
- BAn inoperative blower motor.
- CA faulty engine coolant temperature sensor.
- DA low engine coolant level or air in the cooling system.
Show answer & explanationAnswer & explanation
Correct answer: D. A low engine coolant level or air in the cooling system.
The cabin heater relies on hot engine coolant circulating through the heater core. A low coolant level or air pockets in the cooling system can prevent coolant from reaching the heater core, resulting in cold air from the vents.
Why the other options are wrong
- A. Low engine oil level primarily affects lubrication and engine protection, not the cabin heating system.
- B. An inoperative blower motor would result in no air blowing at all, not just cold air.
- C. A faulty engine coolant temperature sensor primarily affects engine management and gauge readings, not directly the heat output.
HVAC Heater Core Function
A small radiator that transfers heat from the engine's hot coolant to the cabin air.
- Part of the engine's cooling system.
- Hot coolant flows through its tubes.
- A fan blows air across its fins to heat the cabin.
Memory trick: Coolant Flow is Key to Glow!