Final answer:
Both Technician A's suggestion of low air pressure in the spring brake chamber and Technician B's point about a ruptured spring brake diaphragm could be causes for parking brakes failure on a truck with air brakes. The correct answer is (C) Both A and B.
Step-by-step explanation:
When troubleshooting a failure to apply parking brakes on a truck with air brakes, it is critical to understand the mechanisms behind the braking system. A truck's air brake system typically includes a spring brake chamber which is designed to apply the parking brakes when air pressure is released. If a parking brake fails to engage, there could be several causes.
Technician A suggests that low air pressure in the spring brake chamber could be the reason for the failure. This scenario is plausible because the spring brake chamber requires sufficient air pressure to release the spring-applied brakes. If the air pressure is not maintained, the spring cannot be kept retracted, and therefore, the brake will not apply properly.
On the other hand, Technician B points to a ruptured spring brake diaphragm as a potential cause. The diaphragm is an essential component that moves in response to changes in air pressure, controlling the application and release of the brakes. A rupture in this diaphragm could lead to a loss of air pressure control, preventing the spring from being held back, and thus, the parking brakes from engaging.
Taking into consideration both scenarios, it is evident that both technicians present valid points that could lead to the failure of the parking brakes. Therefore, the correct answer to this question is (C) Both A and B.