The air compressor runs continually while the engine is running. The actual compression of air is controlled by the governor actuating the air compressor unloader mechanism. The air compressor unloader mechanism stops or starts the compression of air under the following conditions:
| • | When the maximum reservoir pressure is reached |
| • | When the minimum reservoir pressure is reached |
The governor directs compressed air to the unloader assembly when the air pressure in the system reaches the governor cut-out pressure. The unloader pistons move and hold the inlet valves open. With the inlet valves open, the compression stroke can not occur. The governor exhausts air from the unloader assembly when the air pressure in the system drops to the governor cut-in pressure. The unloader springs move the pistons back to the normal positions and allow the inlet valves to function normally.
