Worcester Bosch 35 RSF Fault codes & diagnostics

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

Combi Natural Gas 35 kW Discontinued
GC Number 47-311-13

Replaced by: 35 CDI

Download the Worcester Bosch 35 RSF 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.
1 Emergency 6 High 1 Low
Just want the most common Worcester Bosch 35 RSF faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 8 documented codes

Tap any card for details

202

Your boiler is currently on standby because it has received a signal from your thermostat to start heating and is preparing to fire up.

Low DIY-safe

What to check first

  1. Check that your room thermostat is set to the desired temperature
  2. Ensure your heating programmer or timer is set to an 'ON' period
  3. Wait a few minutes for the boiler to complete its pre-ignition safety checks

Related codes

Full explanation for 202
235

Your boiler's computer brains are not speaking the same language and need a software update or a component reset to work together correctly.

High Engineer only £120-£350

Parts commonly replaced

  • Heat Control Module (HCM)
  • Electronic Control Board (PCB)
Full explanation for 235
360

Your boiler's internal computer chips are not communicating correctly or do not match, preventing the system from starting up.

High Engineer only £180-350

Parts commonly replaced

  • Heat Control Module (HCM)
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 360
A1

Your boiler has detected that there is not enough water circulating through the system, which could be caused by a leak or a pump that has stopped working.

High DIY-safe £180-450

What to check first

  1. Check for any visible water leaks around the boiler or radiators
  2. Ensure the system pressure is topped up to 1.5 bar using the filling loop
  3. Try restarting the boiler to see if the pump clears itself

Parts commonly replaced

  • Circulation Pump
  • Pump Head
  • Auto Air Vent

Related codes

Full explanation for A1
A8

Your boiler has lost its connection to the external heating controls, meaning the thermostat and the boiler are no longer talking to each other.

High Engineer only £90-180

Parts commonly replaced

  • FX RF Receiver
  • External Temperature Sensor
  • Control Wiring

Related codes

Full explanation for A8
E2

Your boiler's internal thermometer that measures the temperature of the water heading to your radiators has developed a fault and is providing an incorrect reading.

High Engineer only £90-160

Parts commonly replaced

  • Central Heating Flow NTC Sensor
  • Sensor Wiring Harness
Full explanation for E2
EA

Your boiler has stopped working because it cannot light the burner, which is usually caused by a problem with the gas supply or the ignition system within the unit.

High DIY-safe £120-350

What to check first

  1. Check if your gas meter has credit and that the main gas lever is turned on.
  2. Try to relight other gas appliances, like a hob, to confirm there is a gas supply to the house.
  3. Press and hold the reset button for five seconds once gas supply is confirmed.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Flame Sensing Lead
  • Printed Circuit Board (PCB)

Related codes

Full explanation for EA
FA

Your boiler is still detecting a flame even though it has tried to turn the gas supply off, which is a significant safety concern.

Emergency Engineer only £180-£350

Parts commonly replaced

  • Gas valve
  • Detection electrode
  • Printed Circuit Board (PCB)

Related codes

Full explanation for FA
Status & diagnostic codes

4 operating states & engineer diagnostics

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

200 Status Your boiler is not suffering from a fault; it is simply indicating that it is currently operating to provide central heating for your home. 226 Diagnostic Your boiler is displaying a status message indicating that a professional diagnostic tool was recently plugged into the system's internal memory menu. Light on Status Your boiler is working normally and is currently heating your home as requested by your thermostat. rE Status Your boiler is currently resetting itself or stuck in a restart sequence, which usually happens after a fault has been detected or the reset button has been held down.