There is a permanent magnet inside the solenoid valve. When the automatic transmission oil is too dirty, when the transmission oil flows through the solenoid valve, the magnetic field may absorb metal particles in the oil, causing the hole of the solenoid valve to be blocked, resulting in the failure of the mechanical system or hydraulic system. Although the fault code is not displayed, it will cause unstable shifting, delayed shifting, or even failure to shift. When the solenoid valve is activated by battery voltage, it should respond quickly under normal circumstances, but the solenoid valve in question will move slowly and make a blunt knocking sound. Do not connect the positive and negative wires of the power supply in reverse, otherwise, it will cause damage to the solenoid valve diode. The solenoid valve needs to be inspected in four aspects: tightness inspection, voltage inspection, resistance value inspection, and solenoid valve mechanical movement inspection.
Use 0.5MPa compressed air to check the tightness, and the solenoid valve should be able to ensure complete sealing when it is in the closed state.
The automatic transmission clutch actuator solenoid valve is divided into two types: switch type solenoid valve and pulse type solenoid valve from the internal structure. The on-off solenoid valve can be directly connected to the battery, and the solenoid valve will make a "da" sound every time it is powered on. If the sound is not heard or sometimes, it must be replaced. Due to the small resistance value of the pulse solenoid valve, it cannot be directly connected to the battery when performing voltage detection, otherwise the electromagnetic coil of the solenoid valve will be burned. When testing, the battery is usually connected in series with a low-resistance resistor, and then connected to the solenoid valve coil. When the power is turned on, the solenoid valve should make a "click" sound, and at the same time, the solenoid valve spool protrudes outward. The solenoid valve spool retracts inward after power failure. If it is abnormal, it means that the solenoid valve is damaged and needs to be replaced. Generally, the starting voltage of the solenoid valve is 12V, but there are also solenoid valves with a lower starting voltage.
The resistance values of electromagnetic valves of the hydraulic clutch actuator produced by different companies are different. For example, the normal resistance values of various electromagnetic valves in Toyota's transmissions are all 11~150, and the main oil pressure solenoids on Volkswagen's 01N, 01M, and 01P transmissions The resistance value of valve and lock-up solenoid valve is 45~65Q, the resistance value of pressure accumulation buffer solenoid valve and shift solenoid valve is 55~65Q, the solenoid valve of the transmission of the three major companies in the United States, except the resistance value of the main oil pressure solenoid valve Except for 5Q, the rest are mostly 20~30Q at 20°C.
Due to the special working principle of the solenoid valve of the automatic actuator, it is easy to absorb metal debris when it is working, causing the plunger of the solenoid valve to be blocked, resulting in cutting off the normal working oil circuit. Therefore, the ventilation method can be used to check whether the movement of the solenoid valve plunger is smooth. Remove the solenoid valve, ventilate it with an air pump, and check whether its sealing condition and movement are smooth. Normally closed solenoid valve, gas cannot pass through the valve body without power on. If the solenoid valve is connected to a 12V power supply (the solenoid valve is activated), the sound of the plunger movement of the solenoid valve can be heard, and at the same time, the gas can be felt passing through the solenoid valve body. The inspection of the normally open solenoid valve is contrary to the above results.