📊 Vaillant Error Codes — Full Reference Table
| Code | Meaning | DIY Fix? |
|---|---|---|
| F.28 | Ignition failure — no gas or ignition fault | Check gas supply only |
| F.29 | Flame loss during operation | Reset — call if persists |
| F.75 | Pressure sensor / pump fault | Check pressure, call engineer |
| F.22 | Low water pressure | Repressurise system |
| F.24 | Temperature rise too fast — possible pump fault | Call engineer |
| F.83 | Flue temperature sensor fault | Call engineer |
| F.61 | Gas valve regulation fault | Call engineer urgently |
| S.04 | Boiler in anti-cycling mode (normal) | No action needed |
| S.06 | Boiler in freeze protection mode | Check heating, no action |
🔥 F.28 and F.29 — Ignition Faults (Most Common)
F.28 means the boiler failed to ignite. F.29 means the flame went out during operation. These are the two most common Vaillant fault codes.
What to try first:
- Check other gas appliances — does your hob work? If not, call National Gas Emergency: 0800 111 999
- Press the Reset button (🔄 symbol) on the boiler display
- Wait 30 seconds and see if it fires up
If F.28 or F.29 keeps returning after 2-3 resets: Stop resetting. Repeated reset attempts can damage the gas valve. Call FE Maintenance on 020 8445 1303 for a same-day diagnosis.
Common causes requiring an engineer:
- Faulty ignition electrode or lead
- Blocked or dirty burner
- Faulty gas valve
- Printed circuit board (PCB) fault
💧 F.22 and F.75 — Pressure Problems
F.22 is a simple low pressure fault — your boiler pressure has dropped below the minimum. F.75 is more serious — it suggests the pressure sensor or pump may be faulty.
Fixing F.22 — How to repressurise your Vaillant boiler:
- Switch the boiler off and let it cool
- Find the filling loop (flexible hose under the boiler)
- Slowly open both valves until the pressure gauge shows 1.0-1.5 bar
- Close both valves tightly
- Press Reset on the boiler
If your Vaillant keeps losing pressure: You likely have a small leak somewhere in the system — radiator valve, pipe joint, or expansion vessel fault. FE Maintenance can diagnose and fix the source.
Frequently Asked Questions
F.28 on a Vaillant boiler means ignition failure — the boiler tried to light but couldn't detect a flame. Try pressing the reset button once. If it keeps showing F.28, call FE Maintenance on 020 8445 1303 — the ignition electrode, gas valve or PCB may need replacing.
Press the Reset button (flame/reset symbol) on the front panel and hold for 3 seconds. The display will show the reset procedure. If the fault code returns within a few minutes, there's an underlying problem that needs a Gas Safe engineer.
F.75 indicates a fault with the pressure sensor or circulation pump. The boiler cannot detect correct water pressure. This requires a Gas Safe engineer — the pressure sensor or pump may need replacing. Call FE Maintenance on 020 8445 1303.
No — S.04 is a status code, not a fault. It means the boiler is in anti-cycling mode, which is normal operation. The boiler is just waiting a few minutes before firing again to prevent short cycling. No action needed.
Simple fixes like pressure or ignition reset: £80-150. Ignition electrode replacement: £100-200. Gas valve replacement: £250-400. PCB replacement: £250-450. FE Maintenance provides fixed price quotes before starting any work.
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