The exhaust brake system increases the amount of power that is absorbed by the engine when the following conditions exist:

1. The exhaust brake system is turned on.
2. The vehicle is coasting.
3. The clutch is engaged.

The exhaust brake system consists of the following components:

Current flows through the fuse to the clutch pedal switch when the ignition switch is in the ON position. The clutch pedal switch and the accelerator switch are normally closed.

Current flows to the control switch when the clutch and the accelerator pedals are in the released position. When the clutch and the accelerator pedals are in the released position, the engine is at idle and the clutch is fully engaged.

Current flows to the control valve and to the indicator lamp when the control switch is turned ON.

The following actions occur when the control valve is energized:

1. The control valve opens.
2. The open control valve allows air to flow from the brake system air line to the air cylinder.
3. When the air cylinder is supplied with compressed air, the air cylinder pushes the exhaust manifold valve shut.
4. The exhaust pressure allows the engine to become a more effective brake.

The following actions occur when the clutch or the accelerator pedal is pushed in:

1. The accelerator pedal switch or the clutch pedal opens.
2. The power supply to the control valve is interrupted.
3. The control valve closes. This action removes air pressure from the air cylinder.
4. The air cylinder pulls the exhaust manifold open.
5. Normal engine operation resumes.