High
F.33 on Vaillant ecoTEC exclusive 835 VUW 356/5-7

Your boiler has detected an issue with the airflow or flue system, meaning it cannot safely remove combustion gases and has temporarily stopped working.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

Air/flue gas pressure implausible - Check: Cable harness, vacuum hose (blockage), supply air/flue gas route (blockage), panel (correct type), flue pipe (length), air pressure sensor, settings (if necessary, switch D.132 to multiple-flue configuration), pressure switch, fan.

From this model's manual
Verified against the Vaillant/Vaillant Ecotec Exclusive 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.

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 →F.34View →F.36View →

All 207 fault codes on the ecoTEC exclusive 835 VUW 356/5-7

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

conF.00F.00F.01F.01F.02F.02F.03F.03F.10F.10F.11F.11F.12F.12F.13F.13F.20F.20F.22F.22F.23F.23F.24F.24F.25F.25F.26F.26F.27F.27F.28F.28F.29F.29F.32F.32F.35F.35F.42F.42F.49F.49F.55F.55F.56F.56F.57F.57F.61F.61F.62F.62F.63F.63F.64F.64F.65F.65F.67F.67F.68F.68F.70F.70F.71F.71F.72F.72F.73F.73F.74F.74F.75F.75F.77F.77F.78F.78F.80F.80F.81F.81F.82F.82F.83F.83F.84F.84F.85F.85F.90F.90F.94F.94P.00P.01P.02P.04P.06P.14S.00S.01S.2S.02S.3S.03S.04S.05S.06S.07S.08S.09S.09S.10S.10S.11S.11S.13S.13S.14S.14S.15S.15S.16S.16S.17S.17S.19S.19S.20S.20S.21S.21S.22S.22S.23S.23S.24S.24S.25S.25S.26S.26S.27S.27S.28S.28S.29S.29S.30S.30S.31S.31S.32S.32S.33S.33S.34S.34S.36S.36S.37S.37S.39S.39S.40S.40S.41S.41S.42S.42S.46S.46S.53S.53S.54S.54S.55S.55S.56S.56S.57S.57S.58S.58S.59S.59S.76S.76S.86S.86S.88S.88S.92S.92S.93S.93S.96S.96S.97S.97S.98S.98S.99S.99

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