Your Mercedes-Benz has a range of different systems that all play a role when it comes to the temperature control. You have your air conditioning and heater systems that allow you to adjust the temperature of the air in the cabin of your vehicle when you're on the road. The heating system is something that helps direct heat from your engine into the passenger cabin of your vehicle. The heating system is something that can start to wear out over time and display different symptoms that might indicate you need to get replacement parts. If the air coming through your vents is just lukewarm, then you might have a clogged heater core. You can get this flushed out or you can get it replaced if it is too dirty or damaged. If the heater isn't heating up fast enough, this can be a sign of it going out as well. Be sure to invest in OEM heating components for your Mercedes-Benz model.