Control Valves (Heating)

To heat vehicle cabins, most vehicles use the coolant of the engine as a source of heat. The coolant flows through a small heat exchanger called the “heater core”. A fan circulates air through this core when we need heat to warm up the cabin. The heater control valve controls the amount of coolant that flows through the heater core.

The heater core requires no energy to operate, as it recycles residual heat and functions as a small radiator.
The airflow from the blower is controlled by a series of doors inside the blower housing. The control valve enables precise temperature control and dual-zone temperature regulation through multiple doors. When heat is required, air flows through the heater core. Once the passenger compartment is warm, the airflow is diverted around the core.

Most modern systems first cool and dehumidify the air and then heat it to the desired temperature. These valves can be controlled mechanically, by vacuum or electronically.

Three primary faults are responsible for most heater problems:

1. Lack of suitable temperature of the engine
2. Shortage of coolant flow through the heater core
3. Shortage of air flow through the heater core

Symptoms of wear or failure:

• The temperature adjustment might not change the output of the heater
• The valve may lose coolant liquid

Repair recommendations:

• On replacing the heater control valve, all the heater hoses should be inspected and replaced if necessary
• If the heater control valve is being replaced due to corrosion, we recommend cleaning the coolant to avoid additional problems
• The heater control valves are frequently replaced because there are leaks in the hoses. It is recommended that when changing the hoses, the valve should also be changed
• Not all vehicles are equipped with a heater control valve. If a valve is not used, the coolant flows continuously through the heater core and is reheated