Baxi 600 Heat Fault codes & diagnostics

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

Heat Natural Gas 2020-present
GC Numbers 41-470-6641-470-6741-470-6841-470-6941-470-70
Download the Baxi 600 Heat manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
10 High
Versions & GC numbers

Which version do you have?

The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.

GC number Appliance (register name) Produced
41-470-66 613 HEAT 2020–present
41-470-67 616 HEAT 2020–present
41-470-68 619 HEAT 2020–present
41-470-69 625 HEAT 2020–present
41-470-70 630 HEAT 2020–present
Just want the most common Baxi 600 Heat faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 10 documented codes

Tap any card for details

1 green flash

Your boiler has likely sensed that it is getting too hot and has stopped firing to protect itself from damage.

High DIY-safe £100-250

What to check first

  1. Check that your radiator valves are fully open.
  2. Ensure your thermostat is calling for heat correctly.
  3. Restart the boiler by turning the selector switch to the 'Reset' position for five seconds.

Parts commonly replaced

  • Circulation pump
  • NTC Temperature sensor
  • System filter

Related codes

Full explanation for 1 green flash
1 red flash

Your boiler has detected a problem with one of its internal sensors, causing it to stop running as a safety precaution.

High Engineer only £100-220

Parts commonly replaced

  • Interruption cable
  • Return temperature sensor
  • Flow temperature sensor

Related codes

Full explanation for 1 red flash
2 green flashes

Your boiler has paused because a safety switch or external control has told it to stop running, often due to an issue with the condensate pipe or a connected external device.

High DIY-safe £80-220

What to check first

  1. Check if the outdoor condensate drainage pipe is frozen or blocked
  2. Thaw a frozen pipe using warm (not boiling) water or a heat pack
  3. Reset the boiler by turning the selector switch to 'R' for five seconds

Parts commonly replaced

  • Condensate trap
  • External safety sensor
  • PCB

Related codes

Full explanation for 2 green flashes
2 red flashes

Your boiler has switched itself off because it has detected it is getting too hot, likely due to a circulation problem or a temporary blockage.

High DIY-safe £90-250

What to check first

  1. Check that your radiator valves are fully open
  2. Ensure your system pressure is between 1 and 1.5 bar (if a gauge is visible)
  3. Perform a manual reset by turning the selector knob to 'R' for five seconds

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • NTC Temperature Sensor

Related codes

Full explanation for 2 red flashes
3 green flashes

Your boiler is struggling to keep its flame lit, causing it 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 meter.
  2. Inspect the condensate pipe outside to ensuring it hasn't frozen during cold weather.
  3. Reset the boiler by turning the selector switch to the 'R' position for five seconds.

Parts commonly replaced

  • Flame Sensing Electrode
  • Gas Valve
  • Ignition Lead

Related codes

Full explanation for 3 green flashes
3 red flashes

Your boiler has failed to light after several attempts, which means it has shut down for safety and cannot provide heating or hot water.

High DIY-safe £100-280

What to check first

  1. Check if other gas appliances, like a cooker hob, are working to ensure gas is being supplied to the property.
  2. If it is freezing outside, check if your white plastic condensate pipe is frozen and thaw it with warm water.
  3. Press and hold the reset button or turn the selector knob to 'R' for five seconds to restart the boiler.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Spark Generator

Related codes

Full explanation for 3 red flashes
4 green flashes

Your boiler is having trouble communicating with the thermostat or its own internal controls, preventing it from starting up correctly.

High DIY-safe £100-350

What to check first

  1. Check if your wireless thermostat has fresh batteries
  2. Ensure the thermostat is within signal range of the boiler
  3. Turn the electrical power to the boiler off and back on to reset the connection

Parts commonly replaced

  • External Thermostat/Receiver
  • Main Printed Circuit Board (PCB)
  • Wiring Loom

Related codes

Full explanation for 4 green flashes
4 red flashes

Your boiler has stopped working because the fan used to clear waste gases is not spinning correctly or communicating with the system.

High Engineer only £250-£450

Parts commonly replaced

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

Related codes

Full explanation for 4 red flashes
5 green flashes

Your boiler is having trouble communicating its internal computer settings, which is preventing it from running properly.

High Engineer only £120-£350

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Parametric Programming Plug

Related codes

Full explanation for 5 green flashes
5 red flashes

Your boiler has encountered a general safety error and has shut itself down to prevent damage.

High DIY-safe £100-350

What to check first

  1. Turn the selector knob to the 'Reset' position and hold for 5 seconds.
  2. Release the knob and wait for the boiler to attempt to restart.
  3. If the red flashes return, do not attempt further resets and call a Gas Safe engineer.

Parts commonly replaced

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

Related codes

Full explanation for 5 red flashes
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