What does the Vaillant D.34 fault code mean?

Your boiler is struggling to accurately measure how fast its internal fan is spinning, which is preventing the system from heating correctly.

How much does it cost to fix Vaillant error code D.34?

Typical repair cost for the Vaillant D.34 fault is £250-480 including labour.

Vaillant D.34 Fault Code: What It Means & How to Fix It

What the manual says

Manufacturer manual

Fan speed actual value

From this model's manual

Verified against the Vaillant/Vaillant Ecotec Plus Pro 839592 05 2006 installation & service manual.

What causes this fault?

This fault occurs when the boiler's control board cannot get a consistent reading of how fast the fan is spinning. The most common reason is a communication failure between the electronic heart of the boiler and the fan motor, often due to loose wiring or a failing motor.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F.32View →D.33View →

All 135 fault codes on the ecoTEC plus 612 R1 VU GB 126/3-5

Seeing a different code? Every code this model can display, in one place.

35 96 con Connection D,11 D.0 D.1 D.2 D.3 D.4 D.5 D.7 D.8 D.9 D.10 D.12 D.13 D.17 D.18 D.20 D.22 D.23 D.25 D.27 D.28 D.30 D.33 D.35 D.40 D.41 D.44 D.47 D.50 D.51 D.60 D.61 D.64 D.65 D.67 D.68 D.69 D.70 D.71 D.72 D.75 D.76 D.77 D.78 D.80 D.81 D.82 D.83 D.84 D.90 D.91 D.93 D.96 D.97 F.0 F.1 F.10 F.11 F.13 F.20 F.22 F.23 F.24 F.25 F.27 F.28 F.29 F.32 F.49 F.61 F.62 F.63 F.64 F.65 F.67 F.70 F.71 F.72 F.73 F.74 F.75 F.76 F.77 F.78 F70 P.0 P.1 P.2 P.3 P.4 P.5 P.6 S. 2 S. 5 S.0 S.1 S.3 S.4 S.6 S.7 S.8 S.10 S.11 S.13 S.14 S.15 S.16 S.17 S.20 S.21 S.22 S.23 S.24 S.25 S.26 S.27 S.28 S.30 S.31 S.32 S.34 S.36 S.41 S.42 S.52 S.53 S.54 S.96 S.97 S.98

Your boiler is struggling to accurately measure how fast its internal fan is spinning, which is preventing the system from heating correctly.

What the manual says

What causes this fault?

Engineer required

Avoid the next call-out bill

Related fault codes

All 135 fault codes on the ecoTEC plus 612 R1 VU GB 126/3-5

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