Why has my car heater stopped working?

The first thing to check is your coolant. It’s one of the most common causes of a failing car heater and the most easily rectified. If your coolant level is where it should be, then it could be one of a wide range of alternative issues: electrical or mechanical.

Remember—safety first! Always let the car and its components cool down before examining a hot system for faults. You don’t need a trip to A&E as well as one to the garage.

What are the common causes of a broken car heater?

There’s a faulty valve, switch or thermostat

Risk level – Medium

What to do – Find the faulty component and replace it.

Faulty thermostats are the most common reason for a failing car heater. The thermostat is responsible for ensuring the engine operates at the correct temperature and using the coolant to adjust the levels. If it’s faulty or broken, it affects the heating system as well as your car’s performance.

There are also a few valves that could block or stick over time, and after years of regular use, the controls on your dashboard might have finally jammed or developed faulty connections.

You’ve run out of engine coolant

Risk level – High

What to do – Top up your coolant straight away, and then check for leaks.

When the coolant level drops below a certain point, the hot fluid can’t find its way into the heater core, resulting in a cool cabin. It’s one of the simplest problems to rectify, as most motoring depots will carry pre-mixed coolant for every make and model. However, driving with an overheating engine is dangerous, so don’t take any risks if your temperature gauge is heading into the red.

There could be a blockage in your pipes or heater core

Risk level – Medium

What to do – Replace or refurbish your heater core.

It’s less likely to be a heater core issue than many other causes, but it still happens. If debris or particulates infiltrate your coolant system, they can clog the core, preventing the heat from dissipating.

Your heater fan has broken

Risk level – Low

What to do – Replace the fan if it can’t be repaired easily.

If your heater fan isn’t moving any air, then you’re incredibly unlikely to feel the benefit of the heated air within the system.

There’s an issue with the power supply

Risk level – Low

What to do – Check the fuses and power distribution.

It could be a blown fuse, faulty wiring, or a short in the system. Whichever your problem, they’ll all prevent the fan from powering up and delivering the hot air you need.

How much does it cost to fix a car heater?

It all depends on what’s causing the problem. You could expect to pay anywhere between £250 and £550 for most electrical or mechanical issues—or around a tenner, if your car only needs topping up with coolant.

How do I reset my car heater?

Troubleshooting your car’s heater means checking radiator levels, reservoir bottles, fan vents, and fuses. After that, you’re looking at repairs or replacements requiring specialist tools and experience. In that case, you’re going to need a professional diagnosis.

How do I make the heat in my car hotter?

If your car heating system is in good working order, it should adequately produce the temperatures you need for everyday driving. However, if it fails to heat your car sufficiently—and the problem isn’t due to any of the topics already discussed—it could be that the hot air is escaping, or there’s a problem with your engine.

What would cause a heater not to turn on?

If your car heater doesn’t turn on at all, the chances are it’s the switch, the power supply, or the fan that has stopped working. Of course, you can try lubricating the switch to bring it back to life, but ultimately, if that doesn’t get things moving, it’s time to call the experts.

What do you do when your heater blows out cold air?

If you aren’t sure where your car heater problem lies, then one of our trusted mechanics will. Book in with Fixter, and we’ll run a diagnostic test or examine your heating system to uncover the issue. Once we know where the problem is, we’ll run you through all the solutions, their costs and have you toasty and warm again in no time.