Heatline Vizo Plus Fault codes & diagnostics

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

Combi Natural Gas 24 kW 2008-2012 Discontinued

Replaced by: Capriz2

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Severity at a glance

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

All 25 documented codes

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E01

Your boiler has tried to light itself but failed, often because gas isn't flowing correctly or the ignition spark isn't working.

High DIY-safe £100-£280

What to check first

  1. Check that your gas pre-payment meter (if you have one) has credit.
  2. Ensure your gas stopcock or isolation valves are fully open.
  3. Check if other gas appliances, like a hob, are working to confirm gas supply.
  4. Press the Reset button once to see if the boiler restarts.

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB (Printed Circuit Board)
  • Flame sensing cable

Related codes

Full explanation for E01
E02

Your boiler has lost its ability to monitor the temperature of your hot water properly, which usually means your taps will only run stone cold.

High Engineer only £90-160

Parts commonly replaced

  • Domestic Hot Water (DHW) Temperature Sensor
  • NTC Thermistor

Related codes

Full explanation for E02
E03

Your boiler has detected an issue with the sensor that monitors the temperature of the water used for your heating, causing the system to stop working for safety.

High Engineer only £100-180

Parts commonly replaced

  • Central Heating (CH) Flow NTC Thermistor
  • Wiring harness / Lead

Related codes

Full explanation for E03
E04

Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually a silver flexible hose) underneath the boiler.
  2. Slowly open the small valve(s) until you hear water flowing into the system.
  3. Monitor the pressure gauge on the front of the boiler until it reaches between 1.0 and 1.5 bar, then close the valves tightly.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure relief valve

Related codes

Full explanation for E04
E05

Your boiler has detected an issue with how it clears waste gases, preventing it from firing up for safety.

High Engineer only £120-280

Parts commonly replaced

  • Air Pressure Switch
  • Fan
  • Venturi Tube

Related codes

Full explanation for E05
F0

Your boiler has detected that the water pressure is outside the safe operating range, causing the system to shut down to prevent damage.

High DIY-safe £0-120

What to check first

  1. Locate the pressure gauge on the front of the boiler to see if it is below 1.0 bar or above 3.0 bar.
  2. If the pressure is too low, use the filling loop handles underneath the boiler to slowly top it up until the gauge reads between 1.0 and 1.5 bar.
  3. If the pressure is too high, bleed a radiator using a radiator key to release water and lower the pressure back to 1.5 bar.
  4. Once the pressure is corrected, restart the boiler to clear the fault.

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for F0
F01

Your boiler has failed to light, which means your heating and hot water will not work until the gas supply is restored or a internal ignition fault is fixed.

High DIY-safe £100-£280

What to check first

  1. Check that your gas meter has credit (if using a prepay meter).
  2. Ensure the gas emergency control valve is in the 'on' position.
  3. Try resetting the boiler by turning the control knob to 'Reset' for 5 seconds.
  4. Check if other gas appliances, like a cooker, are working to confirm your gas supply is active.

Parts commonly replaced

  • Ignition electrodes
  • Gas valve
  • Ignition lead
  • Printed Circuit Board (PCB)

Related codes

Full explanation for F01
F1

Your boiler has switched itself off because it has reached an unsafe temperature and needs to cool down before it can be restarted.

High DIY-safe £90-180

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the boiler pressure is between 1 and 1.5 bar on the gauge
  3. Press the reset button once the boiler has cooled down for 20 minutes

Parts commonly replaced

  • Overheat thermostat
  • Circulation pump
  • Thermal fuse

Related codes

Full explanation for F1
F02

Your boiler has too much water inside it, which has caused the system to shut down for safety.

High DIY-safe £60-180

What to check first

  1. Check that the internal or external filling loop valves are fully closed.
  2. Bleed water from a radiator using a bleed key to reduce the system pressure.
  3. Monitor the pressure gauge to ensured it returns to between 1.0 and 1.5 bar.
  4. Reset the boiler once the correct pressure is reached.

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel
  • Pressure relief valve

Related codes

Full explanation for F02
F2

Your boiler's hot water sensor has malfunctioned, meaning the system can no longer tell how hot your water is or heat it correctly.

Medium Engineer only £90-£160

Parts commonly replaced

  • DHW Thermistor (NTC Probe)
  • Connecting wiring harness

Related codes

Full explanation for F2
Showing 11–20 of 25
F03

Your boiler has tried to light several times but has failed to detect a flame, causing the unit to shut down for safety.

High DIY-safe £100-280

What to check first

  1. Check that your gas emergency control valve is open and you have credit on your gas meter
  2. Check if other gas appliances in your home, such as a hob, are working correctly
  3. Reset the boiler by turning the control knob to the 'Reset' position for five seconds

Parts commonly replaced

  • Ignition electrode
  • Flame sensing probe
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for F03
F3

Your boiler's internal thermometer has stopped working correctly, meaning the system can no longer monitor the water temperature and has shut down as a precaution.

High Engineer only £90-160

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring Harness

Related codes

Full explanation for F3
F04

Your boiler has become too hot and has shut itself down for safety, likely because water is not moving through the system correctly.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar
  3. Try to reset the boiler by turning the control knob to the 'Reset' position for 5 seconds

Parts commonly replaced

  • Circulation pump
  • Overheat thermostat
  • Main Heat Exchanger

Related codes

Full explanation for F04
F4

Your boiler has stopped working because it failed to light a flame or the drainage pipe for waste water is blocked.

High DIY-safe £90-280

What to check first

  1. Check if your gas supply is active (e.g., check other gas appliances or your meter credit).
  2. Inspect the external white plastic condensate pipe for signs of freezing or blockages.
  3. Press the 'Reset' button on the boiler control panel once to see if the fault clears.

Parts commonly replaced

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

Related codes

Full explanation for F4
F05

Your boiler has detected a problem with how it clears exhaust fumes, which has caused it to shut down for safety.

High Engineer only £120-£350

Parts commonly replaced

  • Fan
  • Air Pressure Switch
  • Venturi Tube

Related codes

Full explanation for F05
F5

Your boiler has shut down because it can no longer safely measure the temperature of the exhaust gases leaving the system.

High Engineer only £120-190

Parts commonly replaced

  • Flue NTC sensor
  • Wiring harness
  • Main PCB

Related codes

Full explanation for F5
F06

Your boiler has stopped working because the water pressure in the system has dropped too low to operate safely.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually a silver braided hose with small tap handles under the boiler).
  2. Slowly open both taps to let water into the system while watching the pressure gauge.
  3. Close both taps tightly once the needle reaches between 1.0 and 1.5 bar.

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for F06
F6

Your boiler's outside temperature sensor is broken or sending an incorrect signal, which means the system doesn't know how hard it needs to work to heat your home.

Medium Engineer only £90-160

Parts commonly replaced

  • External temperature probe (Outdoor sensor)
  • Wiring harness

Related codes

Full explanation for F6
F07

Your boiler is having trouble measuring the temperature of your hot water, which usually means the water won't get hot at all.

High Engineer only £90-160

Parts commonly replaced

  • DHW NTC thermistor sensor
  • Wiring harness

Related codes

Full explanation for F07
F7

Your boiler has detected an issue with the fan that clears exhaust gases, preventing it from starting up for safety reasons.

High Engineer only £180-£350

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Full explanation for F7
Showing 21–25 of 25
F08

Your boiler's internal thermometer has stopped working correctly, meaning the system can no longer accurately monitor the temperature of the water being sent to your radiators.

High Engineer only £90-160

Parts commonly replaced

  • Flow NTC Thermistor
  • Connecting wiring harness

Related codes

Full explanation for F08
F8

Your boiler's fan is running at the wrong time, which is preventing the system from starting its safety checks properly.

High Engineer only £180-350

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Fan Assembly
  • Air Pressure Switch

Related codes

Full explanation for F8
F09

Your boiler's internal computer has lost track of the temperature of the water coming back from your radiators, causing the system to stop working for safety.

High Engineer only £90-160

Parts commonly replaced

  • Central Heating Return NTC Sensor
  • Thermistor Wiring Harness

Related codes

Full explanation for F09
F10

Your boiler has stopped working because water is not circulating correctly through the pipes, likely due to a faulty pump or an air bubble.

High DIY-safe £180-350

What to check first

  1. Check that all radiator valves and boiler isolation valves are fully open
  2. Bleed your radiators to release any trapped air from the system
  3. Press the Reset button on the front of the boiler to see if the code clears

Parts commonly replaced

  • Circulation pump
  • Automatic air vent
Full explanation for F10
OC

Your boiler has detected an outdoor temperature sensor and is automatically adjusting its settings to match the weather outside.

Low DIY-safe

What to check first

  1. No action is required as this is an advisory notification rather than a breakdown.
  2. Check your thermostat settings to ensure the heating is coming on at your preferred times.
  3. If you did not intend to have an outdoor sensor, contact a technician to check the wiring.
Full explanation for OC