Sime Brava DGT HE 25 Fault codes & diagnostics

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

Combi Natural Gas
GC Number 47-283-38
Download the Sime Brava DGT HE 25 manualThe official installation and service manual (PDF), the document these fault codes were read from. PDF

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Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 8 High 1 Low
Fault codes

All 10 documented codes

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AL 02

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

High DIY-safe £0-£120

What to check first

  1. Locate the filling loop (a silver braided hose) underneath the boiler.
  2. Open the small valve(s) on the filling loop to allow cold mains water into the system.
  3. Watch the pressure gauge on the front of the boiler until the needle reaches the green zone (typically 1.0 to 1.5 bar).
  4. Close the valve(s) tightly and ensure the boiler resets.

Parts commonly replaced

  • Pressure Relief Valve
  • Pressure Sensor
  • Expansion Vessel

Related codes

Full explanation for AL 02
AL 05

Your boiler has temporarily stopped working because it cannot accurately read the temperature of the water inside the heating system.

High Engineer only £90-180

Parts commonly replaced

  • Central Heating NTC Thermistor
  • Wiring Harness

Related codes

Full explanation for AL 05
AL 06

Your boiler has completely stopped working because it failed to light or stay safely ignited.

High DIY-safe £90-250

What to check first

  1. Check that your gas supply is turned on and other gas appliances like the cooker are working.
  2. Look at your prepayment gas meter to ensure you haven't run out of credit.
  3. Locate the reset button on your boiler and press it firmly for 5 seconds to try restarting the system.

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Printed circuit board (PCB)

Related codes

Full explanation for AL 06
AL 07

Your boiler has automatically shut down because it has detected dangerously high temperatures inside the unit.

Emergency Engineer only £120-250

Parts commonly replaced

  • Safety limit thermostat
  • NTC temperature sensor
  • Automatic bypass valve
  • Circulating pump

Related codes

Full explanation for AL 07
AL 08

Your boiler has tried to light up but cannot detect a flame, so it has safely shut itself down to stop unburnt gas from building up.

High Engineer only £120-250

Parts commonly replaced

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

Related codes

Full explanation for AL 08
AL 10

Your boiler has detected an issue with the sensor connected to your solar water heating system, which means it cannot properly read the temperature of the incoming hot water.

Low Engineer only £90-180

Parts commonly replaced

  • Solar/DHW Inlet Temperature Sensor
  • Wiring Harness

Related codes

Full explanation for AL 10
AL 13

Your boiler has detected that the flue gases are overheating, so it has safely shut itself down to prevent potential damage.

High Engineer only £120-250

Parts commonly replaced

  • Exhaust temperature sensor
  • NTC sensor
  • Primary heat exchanger

Related codes

Full explanation for AL 13
AL 14

Your boiler has detected an issue with the sensor that monitors the heat of the gases leaving your system, which prevents the boiler from running to keep it safe.

High Engineer only £120-200

Parts commonly replaced

  • Flue temperature sensor
  • Wiring harness

Related codes

Full explanation for AL 14
AL 15

Your boiler has detected that the internal mechanism responsible for venting exhaust gases is not spinning correctly, causing the system to stop working as a safety precaution.

High Engineer only £150-300

Parts commonly replaced

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

Related codes

Full explanation for AL 15
ALL 06

Your boiler has safely locked itself out because it tried to start up three times but failed to detect a flame, usually due to a temporary gas supply issue.

High DIY-safe £90-250

What to check first

  1. Check if other gas appliances in your home (like the hob) are working to confirm your gas supply is on.
  2. Locate your prepayment gas meter to ensure credit has not run out, if applicable.
  3. Locate the reset button or turn the mode selector to the reset position on your boiler, hold it for 3 seconds, and let the boiler attempt to restart.

Parts commonly replaced

  • Ignition lead
  • Electrodes
  • Gas valve

Related codes

Full explanation for ALL 06
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