Low
D.84 on Vaillant ecoTEC pro 28

Your boiler is simply letting you know that it is due for its routine annual service soon.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Maintenance indicator – number of hours until the next maintenance

From this model's manual
Verified against the Vaillant/Vaillant Ecotec Plus Pro 839592 05 2006 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This code is triggered because your boiler has a built-in timer or run-hour counter that tracks how long it has been since its last professional inspection. It is not a mechanical failure but rather a proactive reminder set by an engineer to ensure the appliance remains safe and efficient. Once the pre-set time limit is reached, the system displays this notification to nudge you to book your annual maintenance.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

S.31View →

All 135 fault codes on the ecoTEC pro 28

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

3596conConnectionD,11D.0D.1D.2D.3D.4D.5D.7D.8D.9D.10D.12D.13D.17D.18D.20D.22D.23D.25D.27D.28D.30D.33D.34D.35D.40D.41D.44D.47D.50D.51D.60D.61D.64D.65D.67D.68D.69D.70D.71D.72D.75D.76D.77D.78D.80D.81D.82D.83D.90D.91D.93D.96D.97F.0F.1F.10F.11F.13F.20F.22F.23F.24F.25F.27F.28F.29F.32F.49F.61F.62F.63F.64F.65F.67F.70F.71F.72F.73F.74F.75F.76F.77F.78F70P.0P.1P.2P.3P.4P.5P.6S. 2S. 5S.0S.1S.3S.4S.6S.7S.8S.10S.11S.13S.14S.15S.16S.17S.20S.21S.22S.23S.24S.25S.26S.27S.28S.30S.31S.32S.34S.36S.41S.42S.52S.53S.54S.96S.97S.98

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