Do latching solenoids stay open without continuous power in Allison ATEC/CEC transmissions?

Do latching solenoids stay open without continuous power in Allison ATEC/CEC transmissions?

• A. Yes
• B. No
• C. Only When Commanded
• D. They Are Mechanical and Do Not Use Electricity

Answer: (B)

The actuation in these transmissions relies on a hydraulic valve moved by a solenoid, but the state of that valve isn’t kept solely by the magnetic latch once power is removed. Even a latching solenoid is fighting hydraulic pressure, spring biases, and internal tolerances. A short power pulse can move the valve to the desired position, but when the current is removed, the forces pushing toward the default state (usually closed or neutral) can override the magnetic latch. So the valve is not guaranteed to stay open without continuous power in the Allison ATEC/CEC system. Continuous or periodic energizing is needed to keep the valve in the open state under load, which is why the correct answer is that they do not stay open without power.

The actuation in these transmissions relies on a hydraulic valve moved by a solenoid, but the state of that valve isn’t kept solely by the magnetic latch once power is removed. Even a latching solenoid is fighting hydraulic pressure, spring biases, and internal tolerances. A short power pulse can move the valve to the desired position, but when the current is removed, the forces pushing toward the default state (usually closed or neutral) can override the magnetic latch. So the valve is not guaranteed to stay open without continuous power in the Allison ATEC/CEC system. Continuous or periodic energizing is needed to keep the valve in the open state under load, which is why the correct answer is that they do not stay open without power.