Overview
S.32 on a Vaillant EcoTEC Plus regular boiler is a status code indicating the boiler has detected excessive variation in fan speed and has activated a heat-exchanger antifreeze/protection response. In practice this means the boiler’s combustion-air/ventilation monitoring system is seeing unstable fan behaviour (or a related signal/electronics issue) and the unit has entered a protected state to prevent damage or unsafe operation. On many Vaillant models a similar fault is reported as F.32 (fan fault) when the fan is faulty, blocked or its control/communication is compromised. Severity: medium to high. The boiler may lock out or fail to provide heating and/or hot water while the fault is present. Because the fault involves combustion airflow and internal electronics, it must be treated as a safety-related fault. Initial simple checks can be done by a homeowner, but most diagnostic and repair work (fan replacement, flue/pressure sensor checks, PCB or gas-related work) should be carried out by a qualified Gas Safe engineer. DIY vs professional: homeowners can carry out basic visual and external checks (reset, check air intake and flue, look for obvious blockages or frost on condensate pipe, check boiler pressure and power). Do not open the boiler casing or attempt repairs on gas, electrical, flue or fan components — call a Gas Safe engineer if the code persists after basic checks or if you detect a gas smell or other unsafe signs.
Possible Cause: Heat exchanger antifreeze active as fan speed variation is too high
Troubleshooting Steps
Safety first
1) If you smell gas: do not touch the boiler. Open windows, leave the building and call the emergency gas number immediately. Do not use electrical switches or naked flames.
2) If you are unsure or uncomfortable at any stage, stop and call a Gas Safe engineer. Do not open the boiler or attempt internal repairs.
3) Before any checks, switch off the boiler at the programmer/control and consider isolating power at the external switch. Do not isolate gas unless instructed by emergency services.
Initial homeowner checks (safe, external checks)
1) Note the exact code (S.32), the conditions (cold outside, recent power cut, recent service, when heating was demanded) and take a photo of the display for the engineer.
2) Try a controlled reset: press the boiler fault-clear/reset key for one second (refer to your manual). Wait and see if the boiler attempts to restart. Do not repeatedly reset more than three times; the manual advises limited automatic retries.
3) Check external air intake and flue terminals: ensure the outside vents and flue terminal are clear of snow, leaves, bird nests, debris or external obstructions. A blocked flue/air intake can cause airflow faults.
4) Inspect condensate pipe (in cold weather): if frozen, thaw using warm (not boiling) water or a warm cloth; a frozen condensate can create secondary faults. Ensure any plastic pipework to outside is insulated where required.
5) Check visible wiring/connectors around the boiler (only visually): look for obvious loose connectors or damaged cables at the user interface or external terminals. Do not unplug or probe connectors inside the casing.
6) Check system water pressure on the gauge (should normally be ~1.0–1.5 bar). Extremely low pressure can cause circulation and safety faults; repressurise only if you are familiar with the filling loop procedure.
If the code persists after initial checks
1) Do not attempt to remove the boiler cover or touch the fan or gas components. The likely causes include a failing fan motor, a fan control electronics fault, a damaged fan speed sensor, an air pressure/flow sensor fault, pneumatic hose leaks, or a PCB/electronics fault.
2) Listen for abnormal fan noises when the boiler attempts to start (grinding, stalling, or no sound where you previously heard a smooth fan spin). Do not place fingers near the fan or try to manually spin it.
3) Check whether other error messages or interlock conditions are present (e.g., low pressure, ignition faults). Some multiple faults can mask the root cause. Record all codes and conditions.
What a qualified engineer will do (why a professional is required)
1) The engineer will isolate gas and power and open the boiler safely to access the fan, air pressure switches, pneumatic tubing, connectors and the PCB. They will measure fan speed and control signals, check voltages, and run diagnostic software/LED tests.
2) They will inspect and, if required, replace the fan assembly, repair/replace faulty wiring or connectors, test and replace pressure switches or sensors, and check the flue and air paths for internal restriction.
3) If the PCB or fan-control electronics are at fault, the engineer will advise on replacement. After repairs they will run combustion and safety checks, verify correct operation across modes, clear fault memory, and leave the system safe and tested.
Final notes and practical tips
1) Keep a log of when the fault occurred, resets performed and any environmental conditions (very cold weather, power cuts, servicing). This helps the engineer diagnose intermittent faults.
2) If the fault happens only in very cold weather and you suspect frost, make sure external condensate and intake pipes are insulated and the boiler is allowed to run frost-protection mode. Persistent faults still need an engineer.
3) Do not attempt internal electrical or gas repairs yourself. S.32 relates to combustion air/fan control and electronics — incorrect repair is dangerous and will invalidate warranties.
4) If the boiler repeatedly locks out after reset, call a Gas Safe registered engineer to diagnose and repair the fan, sensors or electronics.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Vaillant EcoTEC Plus Regular Gas Boiler.