The brake lights will be activated when the service brake pressure is greater than 500 kPa (72.5 psi). When the service brake pressure switch detects pressure that is greater than 500 kPa (72.5 psi), the switch closes the contact J1-47 to ground at J1-9. Then, the ECM provides power to the brake lights through contact J2-4 and J2-16.
If the left armrest is in the raised position, the brake lights will not illuminate when the pedal is pressed. When the armrest is raised, contact J1-55 is closed to ground through contact J1-9. The ECM does not allow power to go to the brake lights.
If the armrest is in the down position, the brake lights will illuminate when the pedal is pressed. When the armrest is down, contact J1-54 is closed to ground at contact J1-9. Then, the ECM does not interrupt the normal operation of the brake lights. When the brake pedal is pressed fully, the pedal is locked in place and the operator service brake limit switch is activated.
When the limit switch for the service brake pedal is activated, the service brake is locked and contact J1-57 is closed to ground. When the service brake pedal limit switch is not activated, the service brake is unlocked and contact J1-56 is closed to ground. When the service brake pedal limit switch is activated the ECM starts a 60 second timer. The ECM disables the brake lights after 60 seconds. The ECM assumes that the brake lights are locked because the machine is digging and the brake lights are no longer needed.
Note: If the lights remain on for more than 60 seconds, there could be an overheating condition with the housing of the lights.