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Question #1 of 45

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How can you test the low-pressure warning signal?


There is no way to test a low-pressure warning signal.

Turn the electrical power off and step on and off the brake pedal to reduce air tank pressure. The low air pressure warning signal must come on before the pressure drops to less than 90 psi in the air tank.

Turn the electrical power on and step on and off the brake pedal to increase air tank pressure. The low air pressure warning signal must come on before the pressure increases to more than 60 psi in the air tank.

Turn the electrical power on and step on and off the brake pedal to reduce air tank pressure. The low air pressure warning signal must come on before the pressure drops to less than 60 psi in the air tank.

Turn the electrical power off and step on and off the brake pedal to reduce air tank pressure. The low air pressure warning signal must come on before the pressure drops to less than 30 psi in the air tank.




Inspecting Air Brakes

There are many different system components to check while inspecting air brakes. If the compressor is belt-driven, you will need to check the belt during the pre-trip inspection. The slack adjusters, drums, linings, and hoses must be inspected while doing the walk around as well.

While in the vehicle, you will need to test the air leakage rate, the low-pressure warning alarm, and that the spring brakes come on automatically. You need to test the air pressure build-up rate and the governor cut-in/cut-out pressures as well as performing the service and parking brake tests.

Rather than just studying the correct answers, it is best to learn how the air brake system works and be able to visualize it. This way, the test answers will come naturally, and more importantly, you will have a clear understanding of how the system works, enabling you to be confident and troubleshoot problems in the future correctly.

Air Brake Source: Electronic Code of Federal Regulations.


 

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