Which of the following devices indicates how much pressure you have in your air tanks?
Note
The correct answer is: Supply pressure gauge. All vehicles with air brakes have a supply pressure gauge that indicates how much pressure is in the air tanks. The low air pressure warning signal will only indicate when you have low air pressure (below 60 psi). The application pressure gauge tells you how much pressure you are applying to the brakes. An ammeter is used to measure the amp usage of your electrical systems.