TURBOCHARGER GP 2283228 - Caterpillar

Electronic Speed Switch (ESS)
Illustration 1 g00281790
7W-2743 Electronic Speed Switch (ESS)
Table 1
(1) 75% Verify button.     (4) Seal screw plug for adjusting the overspeed.    
(2) Reset button.     (5) Seal screw plug for adjusting the crank terminate speed.    
(3) LED overspeed light.     (6) Seal screw plug for adjusting the oil step pressure speed setting.    The electronic speed switch (ESS) is a single unit that contains controls which monitor four functions at the same time:
Engine overspeed
Crank termination
Oil step latch
Engine oil step pressureTwo different electronic speed switches are used. The switches are only different in the location of the mounting holes. The ESS is mounted in the junction box.Engine Overspeed (OS)
Engine overspeed is an adjustable engine speed setting. The normal setting is 118% of rated speed. The setting prevents the engine from running at a speed that could cause damage to the engine. An engine speed that is greater than the engine speed setting will close a switch which shuts off the fuel to the engine. If the optional air inlet shutoff is provided, the switch will also shut off the inlet air.Crank Termination
Crank termination is an adjustable engine speed setting that signals the starter motor that the engine is firing and the cranking must be terminated. A switch will open in order to stop the current flow to the starter motor circuit when the engine speed setting is reached. The starter motor pinion gear will then disengage from the engine flywheel ring gear. Oil Step Latch (3500 Series Engines)
The setting of the oil step latch is not adjustable. After (ESS-17) on the terminal strip of the junction box has been energized by the loss of engine oil pressure, the contacts of the oil pressure step switch are held in the closed position. The oil pressure step switch will remain closed until 2 seconds after the engine has completely stopped. This action will prevent the shutoff from resetting below the oil step speed setting. Engine Oil Step Pressure (3500 Series Engines)
Engine oil step pressure is an adjustable engine speed setting that gives protection from engine failure which is caused by too little engine oil pressure for a specified speed range. In order to maintain oil pressure protection throughout the complete speed range of operation, two different engine oil pressure switches are used. Switch (OPS1) has a low pressure rating and switch (OPS2) has a high pressure rating. The engine oil pressure switches are mounted in the engine oil manifold that is located on the rear side of the junction box.The following conditions are for the operation of the oil step latch:
An engine that uses an oil step latch must maintain an oil pressure that is greater than the rating of the low oil pressure switch (OPS1) when the engine runs below the oil step pressure speed setting.
An engine that uses an oil step latch must maintain an oil pressure that is greater than the rating of the high oil pressure switch ("OPS2") when the engine