What does a heater matrix do?
A heater matrix is a small radiator tucked inside the dashboard (usually behind the glovebox) that uses the engine’s hot coolant to warm the air in your cabin. As the engine warms up, hot coolant flows through the matrix via two small hoses. The cabin fan then blows air across the matrix’s fins, picking up heat before that air is directed to the windscreen, face or footwell vents.
Your temperature knob or climate control adjusts this by mixing more or less air through/around the matrix (and on some cars by opening/closing a coolant valve). The A/C evaporator sits in the same air box, so the system can cool and dry the air first, then blend in heat from the matrix for quick, clear demisting.
How do I know I need a heater matrix replacement?
Here’s how to tell when a heater matrix (heater core) likely needs replacing:
- Clear signs of a leaking matrix
- You get a sweet, coolant smell in the cabin, the windows mist up quickly (often with a slightly greasy film on the inside of the windscreen), and the passenger footwell carpet feels damp or sticky. Coolant level in the expansion tank keeps dropping with no obvious leak in the engine bay. In worse cases you might even see fine white “steam” from the vents right after start-up.
Clues it’s blocked (rather than leaking)
The engine reaches normal temperature but the cabin heat is weak or only warm at higher revs, or one side of a dual-zone system blows cooler than the other. Repeated short trips or old coolant can cause this.
Ruling out easy look-alikes first
Low coolant, an air lock, a stuck-open thermostat, a failed heater control valve/blend flap, or a clogged cabin (pollen) filter can all give poor heat without the matrix being bad. If the cabin smells normal and carpets are dry, check these before blaming the matrix.
What a pro will do
They’ll pressure-test the cooling system, inspect the heater hoses, and check flow/temperatures into and out of the matrix. If it’s leaking, replacement is the durable fix; if it’s just partially blocked, a coolant flush might help, but heavy blockage usually means replace. (On many cars the dash needs partial removal, so it’s a labour-heavy job.)
What causes the heater matrix to be blocked?
A heater matrix usually blocks when sludge, scale or debris builds up in its tiny tubes, most often from old/neglected coolant, mixing incompatible antifreezes, topping up with tap water (limescale), using stop-leak products, oil contamination from a failed cooler/head gasket, or debris from failing parts such as the hose lining. Low flow or air locks also let sediment settle and “bake” in. You can prevent this by using the correct coolant at the right strength, changing it on schedule, and avoiding mixing types, tap water, and stop-leak unless it’s an emergency. If cabin heat is weak, a professional back-flush may restore flow, but a heavily clogged matrix usually will need replacement plus fixing the root cause so it doesn’t return.
Can a heater matrix be replaced by a mobile mechanic?
Yes, a mobile mechanic can usually handle the diagnosis, try a back-flush if the matrix is merely blocked, and on a few models replace the heater matrix if it’s accessible from the glovebox/engine bay without removing the whole dashboard or touching the A/C system. However, in some modern cars, they require the air-con to be evacuated to get the matrix out. That means a couple of hours of trim and airbag-safe work, plus refrigerant handling, best done in a garage.
If the vehicle is drivable, ClickMechanic also offers free collection and delivery for bringing the vehicle to a garage.
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Frequently asked questions about heater matrix repair & replacements
Read our answers to questions about heater matrix repair costs, symptoms and more.
What does a Heater Core do?
The heater core is the component within the heating system that actually warms up the air that is circulated through the car. Warm coolant from the engine's cooling system is channeled through the core which heats up the air that is pushed through it by the heater fan. In turn, the air flows out of the air vents and into the cabin, providing warmth for the car's passengers.
What does a heater core replacement involve?
- Mechanic will read the ECU for possible fault codes related to the cooling system.
- Mechanic will inspect the cooling system and the heater core as well as perform a pressure test of the cooling system.
- If necessary, the mechanic will replace the heater core.
- Mechanic will advise if any other parts need to be replaced.
- Mechanic will refill the cooling system.
- Mechanic will bleed the cooling system.
- Mechanic will inspect the heating system once again and check if the heater's temperature is now accurate.
- Mechanic will make any adjustments if necessary.
Can I do a heater core replacement myself?
Unless you are a qualified mechanic with the required skills, training and equipment to do the job, we strongly recommend a heater core replacement is only carried out by a professional mechanic. ClickMechanic can help get you a vetted and local mechanic to carry out the work. Just enter your postcode and your car's registration number at the top of this page and select the work needed to get an instant fixed price up front.
What are the symptoms of a faulty heater matrix?
- When the heater/blower does not work at all (i.e. when there is no air coming from the air vents).
- When the air coming from the air vents is not as warm as usual.
- When there is coolant leaking around components of heating system in the engine bay.
How long will a heater core replacement take?
On average a heater core replacement will usually take around 2.5 hours, but can take anywhere from around 1.5 to 4.5 hours. The time that the job takes will depend on a range of factors. For example, your vehicle's make and model, year, as well as other factors. Select your car at the top of this page for information on job time and cost for your vehicle through ClickMechanic.
How often should I replace a heater core?
Over time, the heater core's effectivity can suffer significantly from contaminated coolant passing through the component. Sometimes the quality of the coolant can deteriorate to such an extent that debris in the coolant can clog up the heater core.
Should you experience problems with the heater core, then it is advisable to have the unit inspected and, if necessary, have it replaced. Remember, it should always be serviced as and when stipulated in the guidelines set out by your car's manufacturer.
Can I drive my car with a bad heater core?
If you suspect there is any issue with the heater core or there are concerns about its age or condition, book an inspection with a professional mechanic as soon as possible. Whilst a faulty heater may not impair the overall performance of the vehicle, it will of course impact comfort.
Is a faulty heater core an MOT failure?
A faulty heater core will most likely not result in an MOT failure as this is not a component tested during an MOT test.
How much does a heater core replacement cost?
On average a heater core replacement costs around £375. Typical prices can range anywhere from £250 to £550. Ultimately, the cost of replacing a heater core depends on your car and what parts your car's manufacturer recommends using for the replacement. Find out what you could save by having a heater core replaced by ClickMechanic by selecting your car at the top of this page!
Check out the ClickMechanic price for a heater matrix repair. See the averages for different makes below. We consolidate industry standard data with millions of data points to give you the most accurate price. These estimates may include Engine coolant/antifreeze and Heater matrix.
| Name | Average Cost | |
|---|---|---|
| Audi | £585 | Get exact price |
| BMW | £813 | Get exact price |
| Citroen | £785 | Get exact price |
| Ford | £1046 | Get exact price |
| Land Rover | £1179 | Get exact price |
| Mercedes-Benz | £847 | Get exact price |
| Nissan | £884 | Get exact price |
| Peugeot | £599 | Get exact price |
| Renault | £947 | Get exact price |
| Toyota | £1200 | Get exact price |
| Vauxhall | £590 | Get exact price |
| Volkswagen | £354 | Get exact price |
Estimates on average repair costs, such as the above results for a heater matrix repair, are based on ClickMechanic's quote data which combines multiple third-party sources. Actual costs may vary. We provide estimates on average repair costs for information only and accept no liability for any inaccuracies or errors. If you think an estimate is incorrect, please contact us to let us know.
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Mechanics that undertake heater matrix work
- AMR, Horsham
- CJ-Autos, Havant
- CPG Auto Solutions Ltd, Romsey
- Car Dealer & WORKSHOP, Weston Super Mare
- DECLAN P, Cleethorpes
- DMC Vehicle Solutions, Midlothian
- Daniel Heath, Manchester
- Hares Servicing & Repairs, Littlehampton
- JARRETTS MOTORS LTD T/A Wilmoths Folkestone, Kent
- JC’s Mechanical Services, Leamington Spa
- K And C Garage, Bristol
- LAP911, Swindon