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When the harsh cold temperatures of winter are upon you, one of the last things you want to go out is your car’s heater. Of all the maintenance issues that could go wrong, a bad heater is probably one of the worst. Here is a short run-down of how your car’s heater works, what could be going wrong with heating core issues, and how to fix those problems. 

The heating system is part of the cooling system

According to Repair Pal, your heating system is part of the cooling system. The cooling system circulates coolant through your engine, where heat is absorbed. Then heated coolant goes through the radiator, and the heat dissipates. The same system also sends heated coolants through the heater core. 

The heater core is located in the dashboard and sends warm air into the car’s cabin once you turn on the heater. Using the controls in the dash, you can control the amount of hot air and what direction it blows. These buttons give directions to the heater valves and blower fan. However, when the heater is not working properly, make sure you take a look at the following possible problems. 

Heater core issues 

The two most likely problems with your heater core are the internal passages and the core exterior. Your car’s heater core is a mini radiator built into the dashboard. It gathers heat from the coolant circulating through the vehicle and then distributes that air through the vehicle. The problem is that there are narrow passages that can get clogged with rust particles or other contaminants. These contaminants can build up over time when the coolant isn’t replaced, or the system is not flushed often enough.

The best solution for the internal passages is for your mechanic to flush out the heater core’s passages. If that doesn’t fit it, then a heater core replacement may be needed. The fins that radiate heat on the outside of the heater core can also get clogged with debris from the outside air intake at the base of the windshield. This can affect the heater’s output. Assuming you can access the heater core, cleaning the debris from the fins and intake passages is best. 

Heater valve issues 

A heater in a 2023 Toyota Camry, which could develop heater core issues.
Car Heater in a 2023 Toyota Camry | Toyota Motor Sales, U.S.A., Inc.

Your car’s heater valves control heat output from the heater core. These valves can be mechanical, vacuum-operated, or electronic. If the heater valve is stuck in a closed position, no hot air can get into the car’s cabin. 

For the mechanical or vacuum-operated heater valves, the problem can typically be fixed by replacing any defective parts. 

However, electronic systems are more complicated to fix. These systems are integrated with the air conditioning system. This more complex system will probably require the professional work of a mechanic to troubleshoot and isolate the problem. The problem could be mechanical or electronic. 

Blower fan issues

One reason you aren’t getting hot air into the cabin of your car could be because the blower fan is not working. Without the blower fan blowing heat from the heater core into your car, you won’t be getting warm while you drive. 

A broken blower fan can be as simple as a blown fuse. It can also be a wiring issue. The worst-case scenario is your blower fan needs replacing. The fix can be simply locating the blown fuse and replacing it. Otherwise, a mechanic will likely need to intervene if the problem is more complicated than that. 


8 Cooling System Issues That Could Mean a Heater Problem and How to Fix It