How to Remove and Replace the Heater Core in the HVAC System on Mazda 6?

This is a difficult procedure for the home mechanic, involving numerous hard-to-find fasteners, clips, and electrical connectors. Have the air conditioning system discharged by an automotive air conditioning technician. Disconnect the cable from the negative battery terminal. Drain the cooling system. Disconnect the heater hoses from the heater core inlet and outlet pipes at the firewall and disconnect the thermal expansion valve and the two refrigerant pipes. Remove the instrument panel. On V6 models, remove the lower cowl grille panel to access some HVAC unit fasteners. Tag and disconnect the cables (if equipped) and electrical connectors from the HVAC unit. Remove the mounting fasteners. The heater core is in the center of the HVAC unit, below the A/C housing. Remove the heater core cover screws and pull the heater core out of the housing. On 2009 and later models, remove the heater core coolant pipe mounting screws, remove the coolant pipes and O-rings from the heater core, then remove the heater core. Installation is the reverse of removal. Don't forget to reconnect the heater core inlet and outlet hoses at the firewall. Use a new gasket where the two air conditioning pipes meet the expansion valve at the firewall. Refill and bleed the cooling system. Have the system evacuated, recharged, and leak tested by the shop that discharged it.

Genuine Mazda 6 Heater Core

HVAC Heater Core

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5 Heater Cores found

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Mazda 6 Heater Core Part Number: GS3L-61-A10
$217.33 MSRP: $289.82
You Save: $72.49 (26%)
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Product Specifications
- Other Name: Core, Heater Unit
- Warranty: This genuine part is guaranteed by Mazda's factory warranty.
Fits the following Vehicles:
- 2009-2013 Mazda 6 | i, S | 4 Cyl 2.5 L GAS, 6 Cyl 3.7 L GAS
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Mazda 6 Heater Core Part Number: GHP9-61-A10
$436.10 MSRP: $586.26
You Save: $150.16 (26%)
Ships in 1-2 Business Days
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Product Specifications
- Other Name: Core, Heater Unit
- Warranty: This genuine part is guaranteed by Mazda's factory warranty.
Fits the following Vehicles:
- 2014-2021 Mazda 6 | Carbon Edition, Grand Touring, Grand Touring Reserve, Signature, Sport, Touring | 4 Cyl 2.5 L GAS
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Mazda 6 Heater Core Part Number: GHR1-61-A10
$428.98 MSRP: $576.69
You Save: $147.71 (26%)
Ships in 1-2 Business Days
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Product Specifications
- Other Name: Core, Heater Unit
- Warranty: This genuine part is guaranteed by Mazda's factory warranty.
Fits the following Vehicles:
- 2014-2017 Mazda 6 | Grand Touring, Sport, Touring | 4 Cyl 2.5 L GAS
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Mazda 6 Heater Core Part Number: GK3J-61-A10
Product Specifications
- Other Name: Core, Heater Unit
- Warranty: This genuine part is guaranteed by Mazda's factory warranty.
Fits the following Vehicles:
- 2003-2008 Mazda 6 | i, Mazdaspeed, S | 4 Cyl 2.3 L GAS, 6 Cyl 3.0 L GAS
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Mazda 6 Heater Core Part Number: GP9A61A10
Product Specifications
- Other Name: Core, Heater Unit
- Warranty: This genuine part is guaranteed by Mazda's factory warranty.
Fits the following Vehicles:
- 2006-2007 Mazda 6 | i, Mazdaspeed, S | 4 Cyl 2.3 L GAS, 6 Cyl 3.0 L GAS

Mazda 6 Heater Core

Mazda 6 Heater Core maintains cabin warmth and cold-free windows by forcing engine heat into the driver's cabin. This small radiator-like device under the dashboard in each Mazda accepts hot coolant via hoses connected to the water pump, and its aluminum or brass fins emit warmth when air is blown through them by the interior blower. The early years of the sedan were based on a basic cable-operated valve allowing more or less coolant to pass through the core, but later 6 models applied electronic actuators and thermistor feedback to adjust the temperature and allowed individual driver/passenger adjustments. The Heater Core can also be applied as a backup radiator, regardless of the generation, which bleeds off additional engine heat when outside temperatures exceed it. With the air conditioning on, the system will first chill and dry cabin air using the evaporator, followed by a slight heat-up using the core to ensure the occupants are provided with dry and comfortable air rather than fogged glass. Since the coolant is constantly recirculated through very small orifices, fluid changes may be overlooked, resulting in rust or scale depositing in the orifices, and the small space under the dash necessitates much interior dismantling to replace it. The highly frequent faults are leaks, electrolytic internal corrosion, and blockages. Mazda owners who feel a sweet odor in the air, wet carpets, or ineffective heating must move with speed to avoid further stress on the engine or damage to the cabin that will extend the life of the Mazda car and its important Heater Core system.

Looking for Heater Core with proven quality? Choose OEM Heater Core. Mazda designs and builds them to strict factory specs. Every piece goes through rigorous quality checks. You'll get parts that fit right and work like new. Shop our huge inventory of OEM Mazda 6 parts. Enjoy the highly competitive prices online. Our site is your one-stop shop. Each genuine 6 part includes a manufacturer's warranty. Buy with confidence. Our return policy is simple and hassle-free. In a rush? Choose expedited delivery at checkout. You'll love the streamlined experience from search to checkout to receiving your order.

Mazda 6 Heater Core Parts and Q&A

Heater Core
GK3J-61-A10
Q: How to Remove and Replace the Heater Core in the HVAC System on Mazda 6?
A:
This is a difficult procedure for the home mechanic, involving numerous hard-to-find fasteners, clips, and electrical connectors. Have the air conditioning system discharged by an automotive air conditioning technician. Disconnect the cable from the negative battery terminal. Drain the cooling system. Disconnect the heater hoses from the heater core inlet and outlet pipes at the firewall and disconnect the thermal expansion valve and the two refrigerant pipes. Remove the instrument panel. On V6 models, remove the lower cowl grille panel to access some HVAC unit fasteners. Tag and disconnect the cables (if equipped) and electrical connectors from the HVAC unit. Remove the mounting fasteners. The heater core is in the center of the HVAC unit, below the A/C housing. Remove the heater core cover screws and pull the heater core out of the housing. On 2009 and later models, remove the heater core coolant pipe mounting screws, remove the coolant pipes and O-rings from the heater core, then remove the heater core. Installation is the reverse of removal. Don't forget to reconnect the heater core inlet and outlet hoses at the firewall. Use a new gasket where the two air conditioning pipes meet the expansion valve at the firewall. Refill and bleed the cooling system. Have the system evacuated, recharged, and leak tested by the shop that discharged it.