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3/a/

Locking fault 3/a/ (2/6/4) - Fan tacho signal failed during operation

Buderus · Logamax plus Boilers

What does 3/a/ mean?

The tacho signal, which monitors the fan's speed, has failed during the boiler's operation. This indicates the fan is not working as expected, affecting combustion and exhaust. This is a locking fault.

Common Causes

  • Faulty fan
  • Fan motor issue
  • Wiring problem
  • Debris in fan

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Allow the boiler to attempt an automatic reset.

  2. 2

    Check for any obvious obstructions around the fan area or in the flue.

  3. 3

    If the fault persists, contact a qualified service technician to inspect the fan and its wiring.

Browse all codes in this manual (43)
Verified technical data. Last updated: April 2026

Related Faults

--/Flashing --/ - Communication fault between UBA 3 and BC10 controller0/y/Locking fault 0/y/ (2/8/5) - Return temperature sensor detected over 203°F (95°C)1/a/Blocking fault 1/a/ (3/1/6) - Flue gas sensor temperature too high
Source: Buderus Logamax plus Boilers
Open Manual (Page 47)Search more codes in this manual