CodeRegistry
Brands
  1. Home
  2. Viessmann
  3. Vitodens 100-W Boiler
  4. F.73
About·Privacy·Terms

CodeRegistry — Your global library for technical solutions.

For your safety: always follow the equipment manufacturer’s official manuals. CodeRegistry is an independent help site and is not affiliated with the brands listed here.

F.73

F.73 — Burner in fault state due to internal communication error

Viessmann · Vitodens 100-W Boiler

What does F.73 mean?

The burner is in a fault state due to an internal communication error. This suggests a problem within the boiler's control system.

Common Causes

  • Internal communication error
  • Faulty BCU burner control unit

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Reset the boiler by briefly turning off and on its power supply.

  2. 2

    If the fault recurs, contact a qualified heating engineer for further diagnosis.

  3. 3

    An engineer may need to replace the BCU burner control unit if the issue persists.

Browse all codes in this manual (60)
Verified technical data. Last updated: April 2026

Related Faults

Connection errorConnection error — Displayed on programming unitF.142F.142 — Burner in fault state due to CAN bus communication errorF.160F.160 — Burner in fault state due to CAN bus communication error
Source: Viessmann Vitodens 100-W Boiler
Open Manual (Page 74)Search more codes in this manual