Why my Mercedes C300 Heat not working?


Mercedes C300 heat not working makes it impossible for you to use the heating function or even start the engine in the cold winter. Do you want to know the cause and how to fix it? Please follow the shares in the article below from experts Eurocartool.

How does the car’s heating system work?

The car’s heating system is responsible for warming the car through the process of radiating heat when the engine operates. Generation The heating system includes the following parts:

  • Grille
  • Hot water tank
  • Water pipe set
  • Water shutoff valve
  • Air divider box
  • Control switch

mercedes-c300-heat-not-working-5 The system will collect heat from the coolant tank after running through the engine. At this time, the temperature will be collected into the water, flowing through the pipe near the dashboard, the fan will blow heated air from the water stream into the cabin for heating.

When activated, this system will not immediately increase the temperature in the car, but only until the car engine is hot enough, the warm air will be slowly blown out.

High-end cars like Mercedes will integrate a heating system in the seats, steering wheel, door handles… This system runs on electric energy so in theory it does not consume much fuel from the car.

Why Mercedes C300 heat not working?

If you turn on the heating mode but after a few minutes you still do not see the temperature increase. It is very possible that the heating system is not working for one of the following reasons, or see Mercedes AC Repair By Yourself Easily To better understand other causes:

Coolant level is low

If the water loss is too low, not enough water will reach the heater core, resulting in the car compartment not being heated.

Thermostat has a problem


This is the reason why the car compartment does not warm up when the heating system is turned on. A faulty or broken thermostat can affect the engine’s cooling system and then Mercedes C300 heat not working.

Temperature sensor error

Modern cars have an electronic coolant temperature sensor that connects to an OBDII computer, so it can inform the temperature gauge. These sensors may be defective. Often they will be flagged when reading OBD error codes.

Heating fan error

The heating fan’s role is to blow hot air into the passenger compartment. When this part is broken or has an electrical problem, it is also the reason why the car’s heating system does not work.

Leaking radiator: A radiator leak prevents coolant from reaching the heating core or even causes damage to the car engine.

Some simple solutions for you

The fastest and best way to fix the mercedes c300 heat not working error is to check and repair the thermostat or temperature sensor. If this part is severely damaged or cannot be repaired, replace it.


If the coolant level is low, you need to refill it properly. To do this, set the car’s heater controls to maximum heat, remove the radiator cap (or pressure cap). The coolant is mounted remotely, sometimes on the overflow tank) and filled to the correct level. Start the engine and, without the cover on, let it idle for a few minutes. Watch for the coolant level to drop as the thermostat opens

In case the Mercedes C300 heat not working cause by broken, start the car to warm up to normal temperature. Check the two heater tubes. If both tubes are hot, the part is not defective. If only one tube is hot, the heating core or control valve is definitely broken and needs to be replaced.


You also need to check carefully for debris beside in the heating box no. Because when there is debris or trash in the heater box, the antifreeze in the system may show signs of leaking through the heater core and create more danger.

In addition to RAM, you should also listen to the sound when adjusting the heat from hot to cold mode. If there is no sound of the mix door moving, this could be a sign of various problems. It could be because the blend door is stuck, the connecting rod isn’t working properly, or the problem is with the wiring or the thermostat switch – everything depends on your vehicle. To make sure Mercedes C300 heat not working will never come and your system running smoothly, regular inspection and maintenance is important.

At this point you can refer How To Fix Mercedes Air Conditioning W222 Not Working?

How to Turn on Heat in Mercedes-Benz

The heating system in Mercedes cars is adjusted using a climate control knob on the center console. Users simply turn the knob left or right to adjust the temperature on the driver and passenger sides including the rear passenger seat.

First, the driver needs to press the defog button on the windshield. The computer will then control and control the heating system’s operation. This system will dispel fog on the windshield and window glass on cold days.


Next, you start the engine system to increase the temperature in the car cabin. The Mercedes C300 heat not working immediately when the defrost button is pressed. Normally the engine must be started and it takes several minutes for the system to take effect. If the vehicle has been used for a long time, the engine has a large capacity, and the outdoor temperature is low, the heating effect will take more time to be effective.

You can easily adjust the desired temperature through the digital display in the car. Some high-end cars are also equipped with temperature control knobs specifically for the front and rear seats.

Many people misunderstand that modern air conditioning systems can cool and heat two ways. Therefore, users often press the A/C button to start the heating system. But in reality, the air conditioner only has one cooling mode and operates independently of the heating system.

Using a heating system does not consume a lot of energy and fuel from the car. By taking advantage of the heat emitted from the operating engine. Besides, the blower motor controls the speed and amount of heat entering the cabin. Therefore it does not consume much energy. The heating system has the ability to direct hot air. Can be adjusted to the driver’s windshield, side windows, passenger’s feet, face area or both depending on the user’s needs.

Mercedes C300 heat not working is a common problem and can be fixed quickly. If you need further advice, experts from Eurocartool will always be available to support you via WhatsApp:+13155472355