Intergas Boiler Error Codes: Causes & Fixes

The most common Intergas boiler error codes UK homeowners and landlords see are 0.0 for low system pressure, code 4 for no flame signal, code 1 for high temperature or overheat, code 8 for fan speed issues, and sensor codes such as 10 to 14 or 20 to 24. 

These codes help you work out what needs attention so you can get the heating and hot water back on safely and quickly.

Some can be sorted with a quick top-up or reset, while others need a Gas Safe registered engineer. Knowing what the code means puts you in control and stops small issues turning into bigger bills. 

Many people find that having reliable boiler cover in place means they can call for help straight away without worrying about the cost of parts or labour when a more serious fault appears.

Intergas Boiler Error Codes: A Quick Overview

Here is a clear snapshot of the Intergas boiler error codes you are most likely to see, with a short plain-English note on what each one usually points to.

Codes can vary slightly by model range, so always check your handbook if the display looks different. The table above covers the codes that appear most often across UK homes.

Intergas Boiler Error Codes: Causes & How to Fix

Below you will find dedicated sections for the main Intergas boiler error codes. Each one explains what the code means, the usual causes, and clear numbered steps you can take. Safety comes first: if you smell gas, turn the supply off at the meter if it is safe and call the National Gas Emergency Service on 0800 111 999. 

For any gas-related work or if a code returns after a reset, contact a Gas Safe registered engineer.

Code 0.0 Low System Pressure

The 0.0 error code means the water pressure in your sealed heating system has dropped below the safe operating level. The boiler will not fire until the pressure is restored.

Common causes include a small leak from a radiator valve, pipe joint or pressure relief valve, natural pressure loss after bleeding radiators, or a problem with the expansion vessel.

1. Check the pressure gauge on the front of the boiler (it should sit between 1.0 and 1.5 bar when the system is cold).
2. Locate the filling loop (usually a flexible silver hose with two valves under or near the boiler).
3. Open both valves slowly to let mains water in until the gauge reaches about 1.2–1.5 bar.
4. Close both valves tightly.
5. The boiler often resets itself. If not, press the reset button.
6. Watch the pressure over the next day or two. If it drops again, there is likely a leak that needs professional attention.

Topping up is a simple job most homeowners can do, but repeated drops should not be ignored.

Code 4 No Flame Signal

The code 4 fault means the boiler has tried to light but the control board has not detected a flame signal. Heating and hot water will stop until the fault is cleared.

Typical causes are a closed gas isolation valve, low gas pressure, a dirty or faulty ignition electrode, a problem with the ignition lead or module, or a blocked condensate drain. In cold weather a frozen condensate pipe is also common.

1. Check that other gas appliances in the home are working. If none are, contact your gas supplier.
2. Make sure the gas isolation valve at the boiler is fully open.
3. Look outside for the condensate pipe and thaw it with warm (not boiling) water if frozen.
4. Press and hold the reset button for a few seconds.
5. If the code returns after one or two resets, switch the boiler off and call a Gas Safe engineer. Do not keep resetting.

Code 1 Temperature Too High

The code 1 means the water temperature inside the boiler has risen too high and the safety system has shut it down.

Common reasons are air in the system, a stuck or failing pump, restricted flow because radiators or valves are closed, or sludge build-up.

1. Turn the boiler off and allow it to cool completely (this can take 30–60 minutes).
2. Check system pressure and top up if needed.
3. Make sure all radiator valves are fully open.
4. Bleed any radiators that feel cold at the top.
5. Reset the boiler once it is cool.
6. If code 1 returns, do not keep using the boiler. Call a Gas Safe engineer to check the pump, flow and heat exchanger.

Code 8 Incorrect Fan Speed

The code 8 error indicates the fan is not running at the correct speed. The fan is essential for safe combustion and removing flue gases.

Causes include a seized or failing fan motor, debris in the fan, wiring issues, or a problem with the control board signal.

Do not attempt to repair the fan yourself. Switch the boiler off and arrange for a Gas Safe engineer to diagnose and replace the fan if needed. Running without a working fan is unsafe.

Code 5 Poor Flame Signal

The code 5 error means the boiler is detecting a flame but the signal is too weak for reliable operation.

Causes include a blocked or frozen condensate drain, incorrect gas valve adjustment, a poor earth connection to the ionisation probe, or back-draught into the flue terminal.

1. Check and thaw the condensate pipe if needed.
2. Reset the boiler once.
3. If the code returns, a Gas Safe engineer needs to clean the electrodes, check the gas valve settings and inspect the flue.

Code 6 Flame Detection Fault

The code 6 error points to a problem with the flame detection circuit.

Causes are usually a faulty ignition cable, spark plug cap, ignition unit or the boiler controller itself.

Reset once if the boiler allows it. If the code returns, an engineer will need to test and replace the affected parts.

Codes 10–14 S1 Sensor Fault

Codes 10 to 14 mean there is a problem with the S1 (flow temperature) sensor.

Causes include a failed sensor, damaged wiring or a poor connection.

This is not a DIY fix. Reset once if possible. If the code returns, an engineer will test and replace the sensor or repair the wiring.

Codes 20–24 S2 Sensor Fault

Codes 20 to 24 mean there is a problem with the S2 (return temperature) sensor.

Causes are similar to the S1 sensor faults. An engineer is required to diagnose and replace the part.

Code 2 Sensors Interchanged

The code 2 error means the flow and return sensors (S1 and S2) have been fitted the wrong way round or their wiring is crossed.

This usually happens after previous work. An engineer needs to check the sensor positions and connections and correct them.

Codes 29 Or 30 Gas Valve Relay Fault

Codes 29 or 30 indicate a problem with the gas valve relay on the control board.

This requires a Gas Safe engineer to test the board and gas valve. Do not attempt any work yourself.

Having a boiler cover plan in place can make a real difference when codes like these appear. Instead of facing unexpected call-out and repair costs, you simply report the fault and a qualified engineer is arranged. For many UK homeowners and landlords this peace of mind, plus the included annual service, helps prevent small pressure or sensor issues from becoming expensive breakdowns.

How To Reset An Intergas Boiler Safely

Most Intergas models have a clearly marked reset button on the control panel. Press and hold it for a few seconds until the display clears or the boiler restarts. Only reset once or twice for the same code. If the fault returns, switch the boiler off and seek professional help. Continuous resetting can put extra strain on components.

When to Stop Resetting Your Intergas Boiler and Call an Engineer

Some Intergas faults can be resolved with basic checks. For example, code 0.0 may be cleared by restoring the correct system pressure, while an ignition fault can sometimes be caused by a frozen condensate pipe or a temporary interruption to the gas supply.

However, there comes a point where resetting the boiler or repeating the same checks is unlikely to solve the problem.

You should contact a Gas Safe registered engineer if:

• Code 4, 5 or 6 keeps returning, as these faults can involve the ignition system, flame detection, gas supply or other combustion-related components.
• Code 1 appears repeatedly, particularly after checking the system pressure, radiator valves and allowing the boiler to cool. This could indicate a circulation or pump problem.
• Code 8 is displayed, as an incorrect fan speed can affect the boiler’s safe combustion and flue operation.
• Codes 29 or 30 appear, as these relate to the gas valve relay and control system.
• Sensor faults such as codes 10–14 or 20–24 continue after a reset, as the sensor, wiring or connection may need to be tested.
• The boiler repeatedly loses pressure after being topped up or develops another fault shortly after returning to normal operation.

Intergas boilers can display a wide range of codes, but recurring faults should not be treated as something to simply reset away. An engineer can trace the underlying cause, test the affected components and make sure the boiler is operating safely before putting it back into regular use.

How to Prevent Intergas Boiler Error Codes

• Keep the system pressure within the normal operating range: Check the pressure gauge periodically, particularly before the heating season. Catching a gradual pressure drop early can help prevent Code 0.0 from causing a boiler lockout.
• Check for signs of a developing leak rather than repeatedly repressurising: If you need to top up the system more than occasionally, look out for damp patches, dripping radiator valves or water from the pressure relief pipe. Ongoing pressure loss should be investigated by a qualified engineer.
• Maintain good water circulation around the heating system: If certain radiators stay cold, heat unevenly or take significantly longer to warm up, address the issue before restricted circulation contributes to overheating or high-temperature faults such as Code 1.
• Bleed radiators carefully when there are signs of trapped air: Gurgling noises and radiators that are cold at the top can indicate air in the system. Removing trapped air and then checking the system pressure can help maintain consistent water flow.
• Protect the condensate drain before freezing temperatures arrive: A blocked or frozen condensate pipe can interfere with normal boiler operation and contribute to flame-related faults. Preparing exposed external pipework for cold weather can reduce the likelihood of this happening.
• Pay attention to weak or unreliable ignition: If the boiler starts taking longer to ignite, occasionally fails to light or locks out intermittently, arrange for the issue to be checked before it develops into a recurring Code 4, Code 5 or Code 6 fault.
• Keep the boiler’s ventilation and flue terminal area unobstructed: Make sure there are no obvious external obstructions around the flue terminal. Never dismantle or modify the flue yourself, but report any suspected blockage or damage to a qualified engineer.
• Do not ignore changes in fan noise: A fan that becomes noticeably louder, quieter or makes unusual mechanical noises may be developing a fault. Having this investigated early can help prevent a complete fan failure and a Code 8 lockout.
• Arrange an annual boiler service: Having your Intergas boiler serviced annually by a Gas Safe registered engineer gives the engineer an opportunity to inspect key components, check for developing faults and identify issues affecting safe and efficient operation before they result in an error code.
• Keep a record of recurring faults and resets: If the same code appears more than once, make a note of when it happens and what the boiler was doing at the time. This information can help an engineer diagnose an intermittent problem more quickly and prevents repeated resets from becoming the long-term solution.

Get Boiler Cover for Unexpected Intergas Faults

While some of the Intergas boiler error codes can be resolved with basic checks or a reset, unexpected faults can still result in the need for professional repairs and unplanned costs.

A PlusHeat boiler cover plan can give you added peace of mind when an unexpected Intergas boiler fault occurs. Instead of worrying about the potential cost of call-outs, parts and labour, you can have cover in place to help protect you against the unexpected.

Explore PlusHeat’s boiler cover plans today and find the right cover for your home or rental property, so you can be better prepared the next time an Intergas boiler error code appears.

Frequently Asked Questions 

What should I do if my Intergas boiler shows a code that is not listed in the manual?

Note the exact code and any lights or symbols, then check the official Intergas support resources or contact a Gas Safe engineer. Different ranges (HRE, Rapid, Xtreme, Xclusive) can use slightly different displays, so matching the full code to your exact model is important.

Can a power cut cause Intergas boiler error codes?

Yes. After a power interruption some boilers display a general sensor fault or lockout. Once power is stable, a single reset often clears it. If the code returns, the control board or wiring may need checking.

How often should I check my Intergas boiler pressure to avoid error codes?

A quick look at the pressure gauge once a month is sensible, especially before winter. Aim for 1.0–1.5 bar when the system is cold. Catching a slow pressure drop early helps prevent code 0.0 from appearing.

Do Intergas error codes differ between combi and system boilers?

Many core codes (pressure, flame, sensors, fan) are shared, but some models may show additional codes related to specific sensors or the burner controller. Always refer to the specific handbook for your model.

Is it safe to keep using the boiler if an error code clears after a reset?

Only if the code does not return and the boiler runs normally with stable pressure and even heating. Any recurring code, unusual noises, or smell of gas means stop using it and call a qualified engineer.