Failure of the compressed air supply to an air brake system is a potentially catastrophic event. Conventional circuitry systems exist to warn of this situation, but they warn only of a low reserve tank pressure. This low pressure reserve air can give at most only a short brake actuation, which may be insufficient to stop the vehicle. The problem is that the warning comes too late- only after the pressure has dropped to a precautionary level.
This invention proposes that warning be given of events which are precursors to loss of pressure, namely events which result in stoppage of the compressor itself. This may reflect a frozen or sheared compressor drive shaft, a broken compressor drive belt, or stripped gears or couplings. All of these events, and others lead to compressor failure, but which will not be noticed by conventional systems until after the system air pressure has fallen, perhaps to an unsafe level. It is an object of this invention to give an earilier warning, increasing the chances for a safe stop.