1321

Check overload relay status

Open electrical cabinet and locate the coolant pump motor starter. Check if the thermal overload relay reset button has popped out or shows a tripped indication.

Ensure machine is powered down and locked out before opening electrical cabinet.

Allow cooling time

Wait 10-15 minutes for the thermal overload relay to cool down before attempting reset. The relay must return to ambient temperature to reset properly.

Feel the motor housing - if it's hot to touch, allow additional cooling time.

Reset overload relay

Press the reset button on the thermal overload relay firmly until it clicks. Power up machine and test coolant pump operation from COOLNT button on control panel.

Monitor motor current

Use clamp meter to measure motor current during operation. Compare readings to motor nameplate amperage - should not exceed 110% of rated current.

Check coolant flow rate

Activate coolant from MDI mode using M08 command. Observe flow rate from coolant nozzles - should have strong, consistent pressure.

Normal flow rate varies by machine model but should produce steady stream, not dribble.

Inspect coolant tank and filters

Check coolant tank level and inspect inlet screen/filter for debris. Clean or replace clogged filters that restrict flow to pump inlet.

Clear coolant line blockages

Disconnect coolant lines at pump outlet and check for obstructions. Use compressed air to blow back through lines to spindle and way covers.

Check pump impeller

If flow remains poor, remove pump cover and inspect impeller for damage or debris wrapped around shaft.

Listen for bearing noise

With coolant pump running, listen for grinding, squealing, or rough running sounds that indicate bearing wear.

Use mechanic's stethoscope or screwdriver against motor housing to isolate bearing noise.

Check motor shaft play

Power down machine and manually check pump motor shaft for excessive radial or axial movement indicating worn bearings.

Measure motor current

Use clamp meter to measure running current. Failed bearings will cause current to exceed motor nameplate rating significantly.

Replace motor or bearings

If bearings are confirmed failed, replace motor assembly or rebuild with new bearings. Ensure proper alignment when reinstalling.

Check motor nameplate data

Record motor full load amperage (FLA) from nameplate. This is the baseline for setting thermal overload protection.

Verify overload relay setting

Check thermal overload relay current setting dial. Should be set to motor FLA or slightly higher (up to 110% of FLA).

Adjust relay setting

If set too low, adjust thermal overload relay dial to proper amperage setting based on motor nameplate FLA.

Test operation

Reset relay, power up machine and test coolant pump operation under normal load conditions to verify proper setting.

Measure supply voltage

Use multimeter to check voltage at motor terminals with pump running. Should be within ±10% of motor nameplate voltage rating.

Check voltage balance

On 3-phase motors, measure all three line voltages. Voltage imbalance should not exceed 2% between phases.

Inspect electrical connections

Check all connections from motor starter to motor for tightness, corrosion, or damage that could cause voltage drop.

Contact electrical utility

If supply voltage is consistently low, contact facility maintenance or electrical utility to correct voltage supply issues.