Ideal Halo Air RF WI FI 2 Zone Fault codes & diagnostics

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

Natural Gas 2020-present

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.
2 High 3 Medium 3 Low
Just want the most common Ideal Halo Air RF WI FI 2 Zone 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

LED / flash-pattern codes
Override Green (flashing)

Your smart thermostat has lost connection with the boiler, causing it to enter a backup safety mode to ensure you aren't left without heat.

Medium DIY-safe £0-120

What to check first

  1. Check if the Halo thermostat batteries need replacing.
  2. Ensure the Halo thermostat is within range of the boiler and has not been moved behind a metal object.
  3. Restart your internet router if the problem persists.
  4. Press and hold the override button on the boiler interface for 3 seconds to attempt a manual reconnect.

Parts commonly replaced

  • AA Batteries
  • Ideal Halo PRT (Thermostat Unit)
  • Ideal Smart Interface RF
Full explanation for Override Green (flashing)
Zigbee Red (flashing)

Your smart thermostat is currently in pairing mode and is searching for a connection to your heating system or internet gateway.

Low DIY-safe

What to check first

  1. Ensure your Smart Interface (connected to the boiler) is also in pairing mode.
  2. Follow the on-screen instructions on your Halo thermostat to complete the setup.
  3. Wait up to 2 minutes for the light to turn solid green, indicating a successful connection.
Full explanation for Zigbee Red (flashing)
Digital codes
CF05

Your heating system is currently trying to establish a link between the heat pump and its control unit.

Low DIY-safe

What to check first

  1. Wait up to 10 minutes for the setup to finish automatically
  2. Ensure the Smart Interface is powered on
  3. If it persists beyond 15 minutes, press the reset button on the interface
Full explanation for CF05
Connectivity Red

Your thermostat has lost its wireless connection to the boiler, meaning your heating controls cannot talk to the system.

Medium DIY-safe £0-120

What to check first

  1. Check that the internet router is switched on and functioning correctly.
  2. Ensure the Smart Interface plugged into the boiler is powered and has a light showing.
  3. Restart the Halo thermostat by removing and reinserting the batteries.
  4. Navigate to the advanced settings on the thermostat to re-pair the device to the interface.

Parts commonly replaced

  • Halo Smart Interface
  • Halo Thermostat
  • Batteries (AA)
Full explanation for Connectivity Red
Halo screen shows Replace Halo

Your thermostat needs to be officially paired or registered with the boiler's receiver to start controlling your heating.

Low DIY-safe

What to check first

  1. Press the 'Accept' button on the Halo screen to confirm this is your primary thermostat
  2. Follow the on-screen prompts to complete the pairing process with the Smart Interface
  3. If the message persists, remove the batteries for 30 seconds and reinsert them to restart the setup
Full explanation for Halo screen shows Replace Halo
HP Comms No illumination

Your smart thermostat is unable to talk to your boiler because the wired connection between them has been lost or disconnected.

High Engineer only £90-180

Parts commonly replaced

  • BSB wiring harness
  • Halo Smart Interface
  • Boiler Control Board
Full explanation for HP Comms No illumination
No illumination (HP Comms)

Your smart thermostat display is blank because it has lost its wired connection to the heat pump or boiler interface, preventing you from controlling your heating.

High Engineer only £90-180

Parts commonly replaced

  • BSB Wiring Connection
  • Ideal Halo Interface
  • Smart RF Hub
Full explanation for No illumination (HP Comms)
Red (Connectivity)

Your smart thermostat has lost its wireless connection to the boiler, meaning you cannot control your heating remotely or via the wall unit.

Medium DIY-safe £0-90

What to check first

  1. Check that your home Wi-Fi router is switched on and working correctly.
  2. Ensure the Halo Smart Interface (the white box plugged into the boiler) has power and is not obstructed.
  3. Navigate to the 'Settings' menu on the Halo unit and select 'Pairing Mode' to reconnect the device to the interface.

Parts commonly replaced

  • Halo Smart Interface
  • Wi-Fi Signal Booster/Extender
Full explanation for Red (Connectivity)