Vaillant Combi Compact 242EB Fault codes & diagnostics

7 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 24 kW 1994-2001 Discontinued
GC Number 47-044-13

Replaced by: Turbomax

Download the Vaillant Combi Compact 242EB manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
4 High 2 Medium 1 Low
Just want the most common Vaillant Combi Compact 242EB faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 7 documented codes

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CONNECTION

Your boiler's main control panel has lost communication with its internal electronic brain, meaning the system cannot receive or process any instructions to work.

High Engineer only £180-450

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Wiring Harness
  • Display Interface

Related codes

Full explanation for CONNECTION
S.1

Your boiler is unable to start its heating process because the internal fan, which safely clears waste gases, is failing to spin up properly.

High Engineer only £180-450

Parts commonly replaced

  • Fan Assembly
  • Air Pressure Switch
  • PCB (Control Board)

Related codes

Full explanation for S.1
S.2

Your boiler is struggling to circulate water properly around the system, which is preventing it from heating up correctly.

High DIY-safe £180-350

What to check first

  1. Check that your boiler pressure is between 1.0 and 1.5 bar on the gauge
  2. Ensure all radiator valves are fully open
  3. Try bleeding your radiators to remove trapped air

Parts commonly replaced

  • Circulating pump
  • Flow pipe sensor

Related codes

Full explanation for S.2
S.3

Your boiler is struggling to light the burner to provide central heating, meaning your radiators will not warm up.

High DIY-safe £120-350

What to check first

  1. Check that your external gas valve is fully open
  2. If you have a prepay gas meter, ensure you have active credit
  3. Try resetting the boiler by turning the main control dial to 'reset' and back

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for S.3
S.6

Your boiler is failing to shut down properly after a heating cycle because the internal fan is stuck running for too long.

Medium Engineer only £120-280

Parts commonly replaced

  • Main PCB
  • Fan assembly
  • Air pressure switch

Related codes

Full explanation for S.6
S.7

Your boiler has finished its heating cycle but is struggling to circulate water to cool itself down correctly, which can cause the system to pause.

Medium DIY-safe £120-280

What to check first

  1. Ensure all radiator valves (TRVs) are fully open to allow water to circulate
  2. Check that the boiler pressure gauge is between 1 and 1.5 bar
  3. Gently bleed air from the radiators if they feel cold at the top

Parts commonly replaced

  • Circulation Pump
  • Overrun Thermostat
  • Bypass Valve

Related codes

Full explanation for S.7
S.8

Your boiler is temporarily pausing the heating because it has reached its target temperature and is waiting for a short period before restarting to prevent unnecessary wear.

Low DIY-safe

What to check first

  1. Check if your room thermostat is set high enough to call for heat.
  2. Wait up to 15 minutes for the 'anti-cycling' timer to finish.
  3. Ensure all radiator valves are open to allow heat to dissipate.

Related codes

Full explanation for S.8
Status & diagnostic codes

2 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

S.15 Status Your boiler is briefly keeping the internal fan and pump running to clear away excess heat after you have finished using hot water. S.O Status Your boiler is currently in standby mode because it hasn't received a signal from your thermostat to turn the heating on.