Parts for your 2020 Mitsubishi Asx-Heater core

2020 Mitsubishi ASX heater core: what it does and how to look after it

A heater core is fitted and very much relevant on the 2020 Mitsubishi ASX. This is documented in Mitsubishi Motors’ Workshop Manual for ASX/RVR/Outlander Sport (2019–2020, Group 55 – Heater, Air Conditioning and Ventilation), which details the “heater core/heater radiator” and its service procedures. It’s also listed in the MMC ASA Electronic Parts Catalogue for 2019–2021 ASX models as “core, heater” within the heater unit assembly. Dealer parts catalogues for the ASX echo the same component and categorisation.

On the 2020 ASX, the heater core acts like a mini radiator inside the dash. Engine coolant runs through it, and the blower pushes air across the fins to deliver warm air into the cabin and help clear a foggy windscreen. It’s a simple bit of kit that quietly does a lot: comfy winter temps, quick demisting, and more consistent cabin climate control when paired with the blend doors and A/C evaporator.

As part of regular servicing, looking after the cooling system is key to keeping the heater core happy. Always use coolant that meets Mitsubishi’s spec in the owner’s manual, keep the coolant at the correct concentration, and replace it at the intervals in the maintenance schedule. Avoid stop-leak products unless it’s a roadside emergency, because they can clog the tiny passages in the core. Swapping the cabin pollen filter on time also helps airflow over the core, so the heater doesn’t feel weak for no good reason. Running the heater for a few minutes every so often (even in warmer months) keeps valves and blend doors moving freely.

• Common signs of heater core trouble: sweet coolant odour in the cabin, greasy film on the inside of the windscreen, poor heater performance, unexplained coolant loss, damp carpet under the dash, or persistent fogging.

If a flush is being considered for a suspected blockage, it should be done thoughtfully: low-pressure reverse-flush only, with the core isolated from the rest of the cooling system to avoid pushing debris elsewhere. If there’s any sign of leakage from the core, replacement is the proper fix.

Replacement on the ASX is a workshop-level job. Access is tight and often involves significant dash disassembly, depending on the procedure followed, the HVAC case may need to be removed, which can mean recovering the A/C refrigerant. Expect more labour than parts cost, and ensure the system is pressure-tested and bled properly after refitting so there’s no air trapped in the core.

Does the 2020 Mitsubishi ASX have a heater core?

Yes. The Mitsubishi Workshop Manual for ASX/RVR/Outlander Sport (2019–2020, Group 55) describes the heater core and its removal/installation steps, and the MMC ASA Electronic Parts Catalogue lists the “core, heater” within the heater unit for this model year.

What are the signs of a failing heater core on a 2020 ASX?

Look for a sweet coolant smell in the cabin, oily mist on the windscreen, weak cabin heat, damp carpet near the front footwells, or steady coolant loss with no obvious external leak. Persistent fogging on cool, damp mornings is another giveaway.

Can a blocked heater core be flushed, or does it need replacement?

A gentle, low-pressure reverse-flush can sometimes restore flow if the core is just restricted. If the core is leaking, replacement is the correct solution. A professional should assess which path makes sense to avoid damaging the core or contaminating the rest of the cooling system.