Usage:
M320 (6WL, 9PS) Excavators
Description of Change: The backup resistors for both the main pump proportional reducing valve (PRV) and the swing pump PRV have a different resistance on the M320 Excavators than on the other M300 Excavators.
The PRV circuit requirements call for a larger backup resistance to meet the backup main pump output. When the backup switch is placed in the ON position, the PRV solenoids are connected to the backup resistors.
Adaptable To: The new 143-8251 Resistors replace the former 124-0329 Resistors for the M320 applications. The new resistors are effective with M320 (6WL187-Up) and M320 (9PS240-Up) Excavators.
The backup resistors for both the main pump proportional reducing valve (PRV) and the swing pump PRV on the M320 Excavator have been changed to new resistors. The backup resistors provide a fixed current to the PRV valve to create a constant PRV valve output signal of 1000 to 1100 kPa (145 to 160 psi). The constant PRV output provides a constant signal to the main and swing pump regardless of the power mode.
The swing pump PRV backup resistor is located in front of the main pump PRV backup resistor when looking at the junction box. The new 143-8251 Resistor for the M320 has a resistance of 59 Ohms compared to the 124-0329 Resistor which has a resistance of 47 Ohms.
View of the junction box to show the location of the resistors.