Why is my mercedes Sprinter heater not working?

Though there are a number of reasons that the Mercedes Sprinter's heater may fail to work, You can typically trace the issue back to problems with the heater blower motor assembly -- including the blower motor itself, or the resistor. Estimates indicate that these two issues combine for around half of all heater failures. Another common occurrence is a failure of the thermostat. You may also have issues with Your heater control valve, one or more of Your heater hoses, or Your blower motor. When You say the heater isn't working, does this also extend to the fan If the heater is just blowing cold air, You're likely looking at temperature regulation, whereas if the fan itself doesn't work, You're looking at something more mechanical in nature.