Correct SR1 Polarization for 7E5585 Junction Box{7426, 1908} Caterpillar

Introduction

For those 3512 Oil Well Service Engines that are equipped with a Caterpillar Electronic Engine Control Governor and the 7E5585 Junction Box, the coil of the SR1 is not being polarized correctly in some instances.

Incorrect polarity effectively forward biases the diode D2, and prevents SR1 from being energized. This will prevent the engine from starting and may damage customer supplied driver circuits.

Polarization Procedure

Care must be taken when connecting the 7E5585 Junction Box to customer wiring. To obtain correct polarization of the SR1, positive (+) 24 volts DC should be connected to TS5 and the battery negative (-) should be connected to TS5A.