Auxiliary Fluid Pump Performance Check: Notes

When checking a low auxiliary fluid pump pressure condition connect the Midtronic 165-PSC charger during testing in order to maintain sufficient battery voltage. A mechanical or electrical concern can cause a low auxiliary fluid pump pressure, or a noise condition. If the auxiliary fluid pump control module is not accurately controlling pump speed there will be a low pressure condition. The following conditions may cause an excessive auxiliary fluid noise condition:

• Mechanical fault within the auxiliary fluid pump.
• Auxiliary fluid pump filter dislodged or restricted.
• High resistance in the 3 phase circuits between the auxiliary fluid pump control module and the auxiliary fluid pump.
• High resistance in the 3 phase circuits within the auxiliary fluid pump control module or the auxiliary fluid pump.

1. Ignition ON, command the auxiliary fluid pump speed to 50 percent with the scan tool. Attempt to maintain pump operation for at least 60 seconds.
2. Compare the auxiliary fluid pump actual and the auxiliary fluid pump commanded displays with the scan tool. The actual pump speed should be within 10 percent of the commanded speed. The pump should not make excessive noise or stall.
   • If the reading is within 10 percent, inspect the auxiliary fluid pump filter for a dislodged or plugged condition.
   • If the difference between actual and commanded speed is greater than 10 percent, the pump is noisy, or the pump stalls, test the 3 phase circuits between the auxiliary fluid pump control module and the auxiliary fluid pump for high resistance. If the circuits test normal, replace the auxiliary fluid pump control module and the auxiliary fluid pump.