Spanner: service due, or an engineer needed
A spanner points to work for an engineer, but makers use it for different things: on Vaillant it means maintenance is due while the boiler keeps running; on Baxi it marks a fault the householder cannot reset.
What the manual says to do
Find out which it is on your boiler. Vaillant: “The product is not in fault mode but continues to operate. Consult a competent person about this”, and if the pressure symbol flashes at the same time, add heating water. Baxi: if a small spanner appears, contact your Gas Safe registered engineer or Baxi and note any error code you have seen. Keep to the annual service your warranty asks for.
Only your boiler’s own manual says exactly what a symbol means on your model. The manuals let the householder reset a fault once, top up the pressure through the filling loop and change the settings; anything else on a gas boiler is a job for a qualified heating engineer (Gas Safe registered in the UK), as the manuals themselves say.
What it does not mean
It is not something to fix yourself. On a Vaillant it does not mean the boiler is unsafe to run: it keeps working until the service. On a Baxi it does not clear with the reset button.
- What it looks like
- A spanner (wrench), alone or beside a code. Vaillant adds a maintenance code such as I.XXX on its current display.
- Names used
- Maintenance required (Vaillant); Spanner symbol: error not resettable by user (Baxi); Service mode (Worcester Bosch); Service menu active (Viessmann)
Where makers differ
Worcester Bosch Greenstar 2000 shows a service-mode symbol only while a qualified service engineer is in the service menus; Viessmann shows ‘Service menu active’. Baxi asks for a service every year, within 60 days of the installation anniversary, to keep the full warranty.
Other symbols with the same shapes
Sources
No public standard defines this boiler symbol, so its meaning is taken from the manuals of 4 different maker groups (Vaillant, Baxi, Worcester Bosch, Viessmann), each fetched and read on the date shown:
- Vaillant, ecoTEC plus VU, VUW, VUI ..6/5-5: Operating instructions ecoTEC plus, 0020245033_02 (26.05.2021) GB, IE (PDF) — “Reading maintenance messages: If the symbol is shown on the display, the product requires maintenance work. The product is not in fault mode but continues to operate. Consult a competent person about this. If the water pressure is flashing at the same time, simply add more heating water.” Checked 2026-09-27.
- Vaillant, ecoTEC plus VU../VUW../VUI.. (current range): Operating instructions ecoTEC plus, 0020308119_03 (28.11.2023) (PDF) — Displayed symbols: “Maintenance required: You can find more information in code I.XXX.” Checked 2026-09-27.
- Baxi, Baxi Compact range (quick guide 7849761): Quick start guide to your boiler, 7849761 Baxi Compact quick guide user instructions (PDF) — Display symbols: “Error – not resettable by user”; “If a small spanner appears, please contact your Gas Safe registered engineer or Baxi Customer Support … Make a note of any error codes”; annual service “within 60 days of the anniversary of the installation”. Checked 2026-09-27.
- Worcester Bosch, Greenstar 2000 combi (GR2301iW): Greenstar 2000 user instructions, 6 721 839 343 (2023/04) UK/IE (PDF) — Screen display: “Service mode — Displays when a qualified service engineer is in the service menus.” Checked 2026-09-27.
- Viessmann, Vitodens 100-W/111-W/111-F/141-F (black/white screen): Operating instructions for the system user, 6167584 GB (12/2020) (PDF) — Symbols in function area A: “Service menu active”. Checked 2026-09-27.
Written in our own words; quotations are the makers’ wording.