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F.88

F.88 - Fault: Gas valve

Vaillant · ecoTEC plus Boilers

What does F.88 mean?

This fault indicates an issue with the gas valve, which controls the flow of gas to the burner. It might not be connected correctly or could have an internal fault.

Common Causes

  • Gas valve not connected or it is connected incorrectly.
  • Short circuit in the cable harness.
  • Gas valve itself is defective.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Press and hold the reset button for more than three seconds to try and clear the fault.

  2. 2

    Do not attempt to inspect or adjust the gas valve yourself due to safety risks.

  3. 3

    Contact customer service immediately. A qualified technician will need to check the gas valve and its connections.

Browse all codes in this manual (146)
Verified technical data. Last updated: April 2026

Related Faults

Communication fault (display/PCB)Communication fault - No communication with the PCBD.092 = 1D.092 = 1 — actoSTOR module connection errorF.0F.0 — Flow–NTC open circuit
Source: Vaillant ecoTEC plus Boilers
Open Manual (Page 34)Search more codes in this manual