Furnace indicates circulation pump fault; no flow through system, radiators remain cold

Safety: Turn off power. For hydronic systems, allow the system to cool before opening any water components.

• Check pump operation: With power on and a heat demand present, place a screwdriver on the pump body and your ear on the handle to listen for humming or vibration. No sound may indicate a failed motor or no power.
• Bleed air: If the pump has a bleed screw, carefully open it slightly with a cloth ready to catch water. Release trapped air until water flows steadily, then retighten.
• Free a stuck rotor: With power off, remove the pump's front plug (if present) and gently turn the rotor shaft with a screwdriver to free it. Reinstall the plug and test.
• Inspect strainer: Some IVT systems include a dirt separator or Y-strainer on the return line. Isolate, depressurize, and clean the strainer screen if clogged.

If the pump still does not run or trips the breaker, it likely needs replacement by a heating professional.