Posted by & filed under Air Conditioning, Fluids, Maintenance, Parts.

The heating system in a car is supplied by hot coolant circulating through the engine. A small amount of hot coolant is diverted into a hose fitted into the firewall and then into a small heater core. Cold air from the outside or recirculated air from the inside is directed through the heater core. A normal working heater will blow air between 75 and 100 degrees. If you are experiencing minimal heat, here are some areas that could be the root of the problem.

Low Coolant Level

A leaky or weak radiator cap can be the problem, but a low coolant level can be the culprit. Check the coolant level in the radiator to see if the radiator is full.

Air Pockets

An air pocket in the heater core or a heater hose may be interfering with the flow of coolant. Check to see if the coolant is circulating through the heater core by feeling both heater hoses. Both the inlet and outlet return hoses should feel hot when the engine is at normal operating temperature and the heater is on.

Open Thermostat

Check to see if the thermostat is stuck open. Start a cold engine and feel the upper radiator hose. You should feel no coolant moving inside the hose until the engine starts to get warm. After a few minutes, you should feel a sudden surge of hot coolant when the thermostat opens.

Defective Heater Control Valve

Vacuum operated heater control valves are normally open unless vacuum is applied. This allows coolant to circulate through the heater core even when the heater isn’t being used. Check the control valve by applying a vacuum with a hand pump. If the valve fails to close, replace it.

Plugged Heater Core

Debris can accumulate in the cooling system which can plug the core and block the flow of coolant. If this happens, it is advised to replace the heater core. To prevent the problem from reoccurring, the cooling system should be flushed and refilled with a 50/50 mixture of antifreeze and distilled water.

Inoperative Airflow Control

If Derhy on December 11, 2014 at 3:45 pm