A20
De Dietrich
Pump Fault / No Circulation
Boiler shows A20, no heating, pump may run, burner off
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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, blocked pump, air-locked pump, faulty pump relay on PCB
How to Fix / Troubleshooting
Safety: Isolate power and allow the boiler to cool before working on the pump. Some water spillage is likely.
- Listen and feel: On a call for heat, place a hand on the circulation pump. You should feel vibration. If silent and cold, it may not be running.
- Bleed pump: Some pumps have a bleed screw. With power off, open carefully to release air and check if the shaft can be turned with a screwdriver.
- Free the impeller: If the shaft is stuck, gently rotate it to free it. Refit the cap and test.
- Technician tasks: If the pump does not receive power or is electrically open-circuit, a technician should replace the pump or repair the PCB.
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Repair Difficulty
Hard
4/5
Required Part
Circulation Pump
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