Operating principle
The information element of the system is a temperature-sensitive switch valve installed in the throttle bodies. When the temperature of the suction passing through the sensor is less than 35°C, the vacuum valve remains open, providing the supply of vacuum in the intake pipeline to the diaphragm of the air thermal valve at the base of the air cleaner housing. Under the influence of vacuum, the diaphragm rises, and the damper blocks access to the cold air air cleaner, leaving only open «hot» channel.
As the air temperature at the inlet to the throttle body rises, the wax-filled capsule of the thermostatic element gradually deforms, which leads to the overlapping of the vacuum switch. As a result, the vacuum supply to the diaphragm stops and the damper begins to lower, blocking the flow of warm air into the air cleaner. At the end of the engine warm-up, only the «cold» channel.
Examination
1. Stop the engine and wait for it to cool completely. Disconnect the intake duct from the front of the air cleaner - the damper should completely block the hot air supply channel. Start the engine: the choke should immediately rise and close completely «cold» channel. As the engine warms up, the damper should slowly lower, gradually closing «hot» channel and opening «cold».
2. To check the functioning of the vacuum switch valve, with the engine off, disconnect the vacuum tube from it and plug it with your finger. With a cold engine, vacuum should be felt in the tube. After the engine has warmed up, the engine compartment should be at normal operating temperature and the vacuum should disappear completely.
3. To check the temperature control valve assembly, disconnect the intake duct from the air cleaner housing - the damper should completely shut off the hot air supply. Disconnect the vacuum tube and, connecting a suitable piece of hose to the fitting, suck in air strongly - the damper should block the cold air supply channel.
4. Defective system components must be replaced. The vacuum switch valve is built into the throttle body cover, the control valve is built into the air filter housing. Individually, these components are not supplied to the aftermarket.
5. After completing the test, restore the original connection of all lines.
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