C15 and C18 – Balance Valve Solenoid Circuit


(34) Balance valve actuator

(35) Line from the intake manifold

(36) Balance valve solenoid

The balance valve solenoid circuit is used to control the balance valve actuator (34) on the turbocharger. Line (35) directs the boost air from the intake manifold to the balance valve actuator. Balance valve solenoid (36) either prohibits or allows airflow to the balance valve actuator (34). Additionally, the engine ECM must send an electronic signal to the balance valve solenoid commanding the solenoid to permit airflow.


Balance valve solenoid in closed position

(37) Path to balance valve actuator

(38) Vent

(39) Armature

(40) Path from the NRS mixer

The balance valve actuator is normally closed. The solenoid must be energized by the ECM to keep the balance valve actuator closed. The armature (1) in the balance valve solenoid is responsible for allowing or prohibiting the pressurizing of the entire balance valve system. The armature physically blocks the boost air from flowing to the balance valve actuator. The vent (2) is responsible for purging residual pressure from the balance valve system once the pressure is no longer needed. Without the vent, there would constantly be pressure on the balance valve actuator and not allow the actuator to close. When the charge air pressure supplied to the balance valve actuator exceeds a predetermined limit, the balance valve actuator will open. The actuator opening causes the turbocharger speed to decrease and protects the engine. Engine speed must be present for in order for the electrical current to command the balance valve solenoid to close. If the key is on but the engine is not running, the balance valve solenoid will remain open.


Balance valve solenoid in open position

(37) Path to balance valve actuator

(40) Path from the NRS mixer

The balance valve solenoid is activated to the open position by the ECM when the conditions of the performance map are met. Typical engine conditions are when the pressure difference between the two turbine paths becomes greater than desired. This conditions can occur during engine powering or engine braking (if applicable). When the balance valve solenoid is open the armature blocks the vent passage, not allowing any leakage.

Posted in C18

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