No Heat, A Cold Weather Complaint
The causes of a no heat condition inside the passenger’s cabin are numerous and varied. There are probably three broad reasons for lack of heat – reduced air flow, reduced coolant flow and low coolant temperature.
Air is forced to the cabin by a fan adjacent to the heater box. It blows against a miniature radiator called a heater core and in the process picks up the heat from the core through which hot coolant flows. The amount of air is adjusted by doors that open or close in the duct work as directed from the dashboard.
The cooling system gets contaminated with all kinds of sludge and precipitants that accumulate in the coolant. This then restricts coolant flow through the heater core which reduces the core’s ability to radiate heat.
It is easy to see how a thermostat that is stuck open and doesn’t allow the coolant to reach operating temperature can reduce the quality of the heat supplied to the cabin. So monitoring engine temp can often be the first clue to what is ailing your car’s heating system.