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Mercedes-Benz C-Class and C-Class AMG: Why is My Heater Not Working?

On older vehicles, having the heat go out is often a precursor to some expensive future repairs. However, with modern cars, the solution is usually more simple. If the heat in your C-Class or C-Class AMG has gone out, read about the required diagnostic work here and get it sorted!

By Brett Foote - May 19, 2015

This article applies to the Mercedes-Benz C-Class and C-Class AMG (2007-2014).

We always expect our air conditioner to blow cold air and our heaters to blow hot air, but what happens when they are no longer operating as they should? It seems that heaters like to stop working when it's incredibly cold outside or in the middle of a long trip. But the good news is, this article provides the information you'll need to diagnose and fix this issue, hopefully before you get too frozen to do so.

Step 1 – Check the blower motor

Has your car given up on blowing any sort of air at all? You might have a bad or stuck blower motor. Once the car is sufficiently warmed up (no longer than 5 minutes or so), the motor should kick on. If not, then you have a problem.

On some early models of the W204 (early 2008 in particular) this was a big problem because the box which the blower is mounted in had no drain holes. Snow and ice buildup can freeze the motor to the point where the fan won't turn at all. You can manually rotate the fan to get it moving temporarily. While there was no recall issued for this problem, it's a known issue that a dealership can easily correct by swapping out the old box with the new, corrected one.

If the blower motor is fine or you thaw it out and it still won't work, check the fuses. A blown fuse in this situation is common if the fan was frozen.

Figure 1. A faulty blower motor will ensure that no air blows in your car.

Step 2 – Check for a squeaky fan issue

Another common issue with several makes and models is a squeaky fan when the HVAC system is operating, usually in colder temperatures. Lubricating the bearing in the blower motor will make this noise go away, as will replacing the assembly. This noise has been known to be a potential indication that the motor is going bad and it might be time for a replacement before a total failure occurs.

If your fan isn't working at all, check your fuses again. This is not an uncommon fuse to have let go, regardless of make/model.

Figure 2. Lubricating the fan bearing can make squeaky noises from the HVAC system go away.

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