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How-To-Troubleshoot-The-A7-Error-Code
Reliability is a hallmark of Worcester Bosch boilers. The same can be said with many other products, from motor cars to trains, boats, and planes. All these products provide a variety of benefits, from comfort, speed, safety, warmth etc. However, like any invention, they occasionally experience performance issues that require troubleshooting. One such issue is the A7 error code in the Worcester Bosch CDi Classic Combi boiler. This fault is commonly associated with a malfunctioning hot water sensor or a problem with the connection to the sensor.


In this blog post, we will explore the A7 error code in Worcester Bosch boilers and guide you through the troubleshooting process.

Understanding The A7 Error Code: Water NTC Sensor Defective

When the A7 error code appears on your Worcester Bosch boiler typically indicates a problem with the water NTC (Negative Temperature Coefficient) sensor. This sensor is responsible for measuring the hot water temperature within the system. When the sensor or its associated wiring is faulty, the boiler may still produce hot water, but the temperature control accuracy may be compromised.

How To Troubleshoot The A7 Error Code.

Step 1: Always Seek Professional Assistance
It is recommended to seek professional assistance with any fault that cannot be rectified outside the white box (boiler casing), i.e., resetting or rebooting the boiler. You are not legally permitted to access the internal working of a gas boiler without Gas Safe qualifications for safety reasons. You must contact an authorised Worcester Bosch service engineer or a qualified heating engineer with Worcester Bosch boiler experience. They will have the expertise and specialised tools to accurately diagnose and resolve the issue.

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Step 2: Reset Your Boiler and Perform Regular Maintenance
Before delving into the specific troubleshooting steps, it's always a good idea to reset your boiler by switching it off and then on again (reboot). This simple action can often resolve temporary glitches or minor issues. In addition, make sure you adhere to the recommended annual boiler service schedule. Regular maintenance can prevent potential problems to ensure optimal performance.

Step 3: Check the Water NTC Sensor and its Connections (This diagnosis should be done by a qualified boiler engineer)

Inspect the Water NTC Connector: Start by examining the NTC connector for any signs of corrosion, damage, or dirt. If you notice any issues with the connector, it may need replacing. Contact your usual gas repair and maintenance company or the manufacturer for assistance in acquiring the necessary replacement parts.

The engineer will disconnect the power and unplug the 20-Pin Connector from the boiler's Printed Circuit Board (PCB).

Test Resistance Values: With the 20-pin connector unplugged, the resistance between connections 3 and 4 on the cable side will be checked. The resistance values will be compared with those specified in Table 39 on page 36 of the boiler's manual. If the measured resistance does not match the specified values, there may be a problem with the sensor or the wiring.

Call A Professional Gas Engineer

Serviceteam Ltd, London, are accredited Worcester Bosch installers and are conversant with every make and model of gas and electric boilers.

Our team of heating engineers is available 24/7, throughout the year, in London, thus ensuring prompt and reliable emergency boiler repair services. If you are experiencing any issues with your boiler, don't hesitate to contact our dedicated help desk or conveniently book your heating engineer online and receive a 5% discount.
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