Glow-worm Ultracom Fault Codes
The Glow-worm Ultracom — cxi combi, sxi system, hxi heat-only — was the brand's better-specified range of the same era as the Flexicom, with plenty still running. It uses the same style of F-code fault reporting on a digital display, spanning ignition, flame supervision, overheat, sensors, fan/flue and pressure faults. Everything true of maintaining a senior boiler applies: wear-driven faults, sludge as the great accelerant, and repair-versus-replace arithmetic once bills stack. The Ultracom's better build gives it a fair chance of justifying repairs a while longer than budget contemporaries. Codes below link to their full pages; where Ultracom generations differ in a code's exact trigger, the linked page and your model-year manual are the authorities.
Where Ultracom fault codes appear
The Ultracom shows F-prefixed codes on its fascia display when faults trip. If the boiler attempts, fails and retries, watch a full cycle — the code shown at the failure moment identifies the fault more reliably than whatever remains on screen later.
Resetting a Glow-worm Ultracom
Press the reset button briefly to clear and retry. Pressure codes want the system at 1–1.5 bar first via the filling loop. A code that survives one reset on a boiler of this vintage merits an engineer visit rather than optimism — wear faults only travel one direction.
Common Ultracom problems
Ultracoms in their senior years log the familiar sequence: ignition-component wear and winter condensate freezes producing lockouts, circulation and overheat codes as pumps and water quality decline, sensor failures with age. Serviced examples with treated water routinely outlast expectations; neglected ones spend their final winters on this page.
Most common Ultracom fault codes
- F1 The F1 code appears on Glow Worm boilers when the boiler has attempted to light itself… Read more →
- F4 The F4 code means your Glow-Worm boiler has failed to detect a flame during the ignition… Read more →
- F9 The F9 fault code on a Glow-Worm boiler indicates that the boiler's control board has… Read more →
- F13 The F13 code appears on Glow-Worm boilers when the main PCB detects a problem with its… Read more →
- F22 The F22 fault code on a Glow-Worm boiler signals that the water pressure inside your… Read more →
- F28 The F28 code means your Glow-Worm boiler attempted to light the burner, failed to detect… Read more →