Intake air temperature control system (models with central injection) — operating principle and serviceability check (Opel Astra G)

Operating principle

The information element of the system is a temperature-sensitive valve-switch installed in the throttle body. When the temperature of the intake air passing through the sensor is less than 35°C, the vacuum valve remains open, providing the supply of vacuum from the intake manifold to the diaphragm of the air thermovalve in the base of the air cleaner body. Under the influence of vacuum, the diaphragm rises, and the flap closes the access of cold air to the air cleaner, leaving only the "hot" channel open.

As the air temperature at the inlet to the throttle body increases, the wax-filled capsule of the thermostatic element gradually deforms, which leads to the vacuum switch being closed. As a result, the vacuum supply to the diaphragm stops and the flap begins to move down, blocking the flow of warm air into the air cleaner. After the engine warms up, only the "cold" channel remains open.

Examination

1. Turn off the engine and wait until it cools down completely. Disconnect the air intake duct from the front of the air cleaner - the flap should completely block the hot air supply channel. Start the engine: the flap should immediately rise and completely block the "cold" channel. As the engine warms up, the flap should slowly fall, gradually blocking the "hot" channel and opening the "cold" one.

2. To check the proper functioning of the vacuum switch valve, with the engine off, disconnect the vacuum tube from it and plug it with your finger. When the engine is cold, a vacuum should be felt in the tube. After the engine warms up to normal operating temperature, the vacuum should completely disappear.



Text copied from an internet website OpelBook.ru

3. To check the temperature control valve unit, disconnect the air intake duct from the air cleaner housing - the damper should completely block the hot air supply. Disconnect the vacuum tube and, having connected a suitable section of hose to the fitting, suck in air strongly - the damper should block the cold air supply channel.

4. Defective system components are subject to replacement. The vacuum switch valve is built into the throttle body cover, the control valve is built into the air filter housing. These components are not supplied to the aftermarket individually.

5. After completing the check, restore the original connection of all lines.