Low
D.078 on Vaillant ecoTEC plus 612

Your boiler is temporarily limiting the temperature of your hot water to protect itself from overheating while it performs an internal system check.

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

DHW max. flow temperature

From this model's manual
Verified against the Vaillant/Vaillant Ecotec Plus 612 4104460 installation & service manual, page 57.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

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

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Related fault codes

F.78View →

All 121 fault codes on the ecoTEC plus 612

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

Communication faultD.000D.001D.002D.003D.004D.005D.006D.007D.008D.009D.010D.011D.012D.013D.014D.015D.016D.017D.018D.019D.020D.022D.023D.025D.026D.027D.028D.033D.034D.035D.036D.039D.040D.041D.044D.046D.047D.050D.051D.058D.060D.061D.064D.065D.067D.068D.069D.070D.071D.072D.073D.075D.076D.077D.080D.081D.082D.083D.084D.088D.090D.091D.093D.094D.095D.096D.098F.00F.01F.02F.03F.10F.11F.12F.13F.20F.22F.23F.24F.25F.26F.27F.28F.29F.32F.35F.42F.49F.52F.53F.54F.56F.57F.61F.62F.63F.64F.65F.67F.68F.70F.71F.72F.73F.74F.75F.76F.77F.78F.83F.84F.85F.91F.92F.93S.11S.16S.17S.24

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