Boiler displays PUMP or Pump Fault; circulator does not run when there is a call for heat.

Safety first: Turn off power before touching the pump or wiring. Pump surfaces may be hot.

• Check pump wiring: Verify that the circulator wires are securely connected at the Laars control and at the pump junction box.
• Feel the pump: With a call for heat and power on, carefully touch the pump housing. If it hums but does not move water, it may be air-locked or seized.
• Bleed air: Use nearby purge valves or air vents to remove air from the pump and piping (with system cool). Air can prevent the impeller from moving water.
• Power test (advanced): A qualified person can check for voltage at the pump terminals when the boiler calls for heat. If voltage is present but the pump does not run, the pump is likely failed.

When to call a professional: Pump replacement and control board relay diagnostics should be done by a heating technician.