P1
Bosch Circulation Pump Fault

Furnace shows P1; burner output limited or unit stops

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Seized circulation pump, Air-locked pump, Electrical failure of pump motor, Blocked pump impeller

How to Fix / Troubleshooting

Safety: Turn off power and allow the system to cool before touching the pump.

  • Check pump operation: With power on and a call for heat, place a screwdriver on the pump body and your ear on the handle to listen for humming or running. No sound may indicate a failed pump.
  • Free a stuck rotor: Many Bosch pumps have a front screw cap. With power off and a towel ready, remove the cap and gently turn the shaft with a screwdriver to free it. Refit the cap.
  • Bleed air: Open any automatic air vents near the pump to release trapped air.

If the pump still does not run or trips breakers, it should be replaced by a technician.

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Repair Difficulty

Hard 4/5

Required Part

Circulation Pump
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