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4/c/

Blocking fault 4/c/ (2/2/4) - No bridging cable between UBA 3 contacts 22 and 24

Buderus · Logamax plus Boilers

What does 4/c/ mean?

There is no bridging cable detected between contacts 22 and 24 on the UBA 3 contact strip. This connection is essential for normal operation. Heating and domestic hot water are unavailable. This is a blocking fault.

Common Causes

  • Missing bridging cable
  • Faulty contact strip on UBA 3
  • Wiring issue

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Press the 'Reset' button on the BC10 basic controller.

  2. 2

    A qualified installer should visually inspect the UBA 3 contact strip for the bridging cable.

  3. 3

    If the fault persists, contact a qualified service technician to check the wiring and UBA 3 unit.

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 48)Search more codes in this manual