Your Mazda’s heater works by using heated air from the engine and directing it into a heater core that pushes it into your car’s interior cabin. Everything involved in this process needs to be functioning properly in order to heat the inside of your car efficiently, or at all. Once your car is up to operating temperature, you’ll know pretty quickly if the heat is working on a cold day or not. Here are some basic steps to troubleshooting Mazda heater issues.
Photo Credit: Ken_Mayer
Start by checking the system for obvious damages, broken parts, and make sure your hoses aren’t split or cracked. Leaks and obstructions are common culprits of heater issues. Repair or replace any parts with signs of damage.
Check your coolant level, add coolant to the system if needed.
Check the blower motor and circuit to make sure the motor is working as it should. Inspect all of the fuses, wire connections, and switches to make sure they are in working order. Checking the resistor will require an ohmmeter, this will tell you if it is giving off current.
If you do need to replace the blower motor, you must first drain the cooling system and follow the instructions in your Mazda service manual carefully.
Hold your hand above the black hoses connecting to the heater core at the firewall, you should feel heat when the engine has warmed. If you don’t feel heat, coolant isn’t circulating as it should and the heater core is likely the problem at this point.
Make sure the rest of your Mazda’s cooling system is working properly. While heater issues are usually not the first symptom, a faulty water pump or bad thermostat will impact the heater. The first sign of these issues will be an overheating car. So if your car is overheating and your heater isn’t working, it’s not the heater core or blower motor, it’s likely another part of the cooling system that's malfunctioning.
Always remember to replace parts with factory Mazda parts to keep your heating system functioning as it should. This will prolong the life of your car’s HVAC system and prevent premature failure from cheaply made aftermarket parts.