700

Common Causes

• Coolant pump mechanical seizure or bearing failure causing excessive current draw when motor attempts to run
• Clogged coolant filter or blocked discharge line creating high back pressure and overloading the pump motor
• Coolant tank debris or chips jamming the pump impeller and preventing normal rotation
• Thermal overload relay calibrated too low or failing, tripping prematurely even with normal pump current draw
• Incorrect voltage supply to pump motor or wiring fault causing single-phase operation on three-phase motor

Troubleshooting Steps

1. 1Step 1: Press RESET to clear alarm and attempt to restart coolant pump using M08 command, listen for abnormal noise or failure to start
2. 2Step 2: Check coolant tank for low level, debris, or foreign material that may be restricting pump inlet or jamming impeller
3. 3Step 3: Inspect coolant filter and clean or replace if clogged with chips or sludge causing restricted flow
4. 4Step 4: Locate thermal overload relay in electrical cabinet (usually mounted near coolant contactor) and press manual reset button if tripped
5. 5Step 5: With pump power disconnected, manually rotate pump shaft or impeller to check for mechanical binding, bearing roughness, or seized condition
6. 6Step 6: Use clamp meter to measure pump motor running current on all three phases and compare to motor nameplate rating, replace pump motor if current is excessive or windings are shorted