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1A

1A — Flow sensor 1 faulty

Viessmann · Vitodens 200-W B2HB Boiler

What does 1A mean?

The burner is blocked because flow sensor 1 is faulty, which monitors the heating water flow.

Common Causes

  • Malfunction of flow sensor 1
  • Damaged wiring to flow sensor 1

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Attempt to reset the boiler by pressing the reset button 'R'.

  2. 2

    Inspect the wiring connections to flow sensor 1 for any visible damage or looseness.

  3. 3

    Contact a qualified heating technician to replace flow sensor 1.

Browse all codes in this manual (56)
Verified technical data. Last updated: April 2026

Related Faults

0F0F — Boiler requires service1010 — Short circuit on outdoor temperature sensor1818 — Outdoor temperature sensor cable broken
Source: Viessmann Vitodens 200-W B2HB Boiler
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