Ferroli Combi 77 FF Popular Fault codes & diagnostics

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

Combi Natural Gas 23.3 kW 1994-2000 Discontinued

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Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 5 High 1 Medium 7 Low
Just want the most common Ferroli Combi 77 FF Popular faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 14 documented codes

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1 green

Your boiler is receiving power and has gone into a standby mode because the incoming electrical voltage is too low for it to operate safely.

Low DIY-safe £0-120

What to check first

  1. Check if there is a power cut or brownout in your local area
  2. Ensure the boiler is plugged into a dedicated socket and not an overloaded extension lead
  3. Turn the boiler power switch off and back on again to reset the electronic logic

Parts commonly replaced

  • None (External power issue)
  • PCB (Printed Circuit Board)
Full explanation for 1 green
2 yellow

Your boiler thinks you are running a hot tap even when they are all turned off, which may cause the heating to stay off or the internal water to overheat.

Medium Engineer only £90-160

Parts commonly replaced

  • DHW flow switch
  • Flow switch diaphragm
  • Microswitch
Full explanation for 2 yellow
3 CH yellow

Your boiler has received a signal from your thermostat or timer telling it to turn the heating on.

Low DIY-safe £0-120

What to check first

  1. Check if your room thermostat is turned up higher than the current room temperature
  2. Ensure your heating programmer or clock is set to an 'ON' period
  3. Replace the batteries in your wall thermostat if the screen is blank

Parts commonly replaced

  • Room thermostat
  • External programmer
  • Clock timer unit
Full explanation for 3 CH yellow
4 green

Your boiler's internal temperature sensors are stuck in a mode that is telling the system to stay on, which can lead to overheating or your heating staying on when it shouldn't.

High Engineer only £90-160

Parts commonly replaced

  • NTC Temperature Sensor
  • Central Heating Sensor
  • Thermistor

Related codes

Full explanation for 4 green
5 red

Your boiler is currently taking a brief, scheduled pause to protect its internal parts before restarting your heating or hot water.

Low DIY-safe

What to check first

  1. Wait for 3 to 5 minutes to see if the boiler restarts automatically
  2. Ensure your room thermostat or programmer is calling for heat
  3. Check that your boiler pressure is between 1 and 1.5 bar
Full explanation for 5 red
6 yellow

Your boiler has received a request to provide heat and is now attempting to start the internal fan to begin the ignition process.

Low Engineer only

Parts commonly replaced

  • Fan
  • Air Pressure Switch
  • Main Control Board (PCB)
Full explanation for 6 yellow
7 green

Your boiler has detected an issue with the air flow or fan, meaning it has stopped working for safety reasons.

High Engineer only £120-280

Parts commonly replaced

  • Air Pressure Switch
  • Fan Assembly
  • Venting Venturi Tube
Full explanation for 7 green
8 yellow

Your boiler has detected that the gas valve is opening at the wrong time or when it hasn't been told to, which is a safety concern that prevents the appliance from running.

Emergency Engineer only £180-350

Parts commonly replaced

  • Gas valve
  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Full explanation for 8 yellow
LED 2 on P.C.B. alight

Your boiler is receiving electrical power, but if the display isn't working otherwise, there may be a blown fuse on the internal circuit board.

Low Engineer only £90-180

Parts commonly replaced

  • 2 Amp Fuse
  • 125 mAmp Fuse
  • Printed Circuit Board (PCB)

Related codes

Full explanation for LED 2 on P.C.B. alight
LED1

Your boiler has detected that the internal air fan or pressure system is stuck in the 'on' position, preventing the boiler from starting its ignition sequence for safety.

High Engineer only £120-£280

Parts commonly replaced

  • Air Pressure Switch
  • Venturi Tube
  • Fan Assembly
  • Main PCB

Related codes

Full explanation for LED1
LED1 on

Your boiler has detected a failure with the safety system that handles smoke and fumes, preventing it from firing up for your safety.

High Engineer only £120-240

Parts commonly replaced

  • Air Pressure Switch
  • Venturi Tube
  • Fan Assembly
Full explanation for LED1 on
LED2

Your boiler is currently receiving electrical power and is in a normal 'standby' mode waiting for a command to provide heating or hot water.

Low DIY-safe

What to check first

  1. Check if your room thermostat or programmer is turned up and calling for heat
  2. Ensure the boiler control knob is set to the correct winter or summer position
  3. Wait 10 seconds to see if the boiler moves into a firing sequence automatically

Related codes

Full explanation for LED2
LED3

Your boiler is currently reading a request to provide hot water or heating, which is a normal operational signal and not a fault unless the boiler fails to fire up.

Low DIY-safe £0-120

What to check first

  1. Check that your room thermostat is turned up to trigger a heating demand
  2. Ensure your programmer or timer is set to an 'On' period
  3. Open a hot water tap fully to see if the boiler responds to the demand

Parts commonly replaced

  • None (Normal operation)
  • Flow Switch
  • Diverter Valve

Related codes

Full explanation for LED3
Relay 2 energised after 2 sec

Your boiler has detected an internal electrical or sensor error that is preventing it from starting up safely.

High Engineer only £120-£350

Parts commonly replaced

  • Main PCB
  • DHW Temperature Sensor
  • DHW Flow Switch
Full explanation for Relay 2 energised after 2 sec