A red light on your boiler may indicate a boiler fault or a fault with a wireless room thermostat. Use this guide to quickly find the source of the fault.
Why is there a red light on my boiler?
In general a red light showing on the boiler is sign that something has gone wrong. The first step is to find where the light is.
Where is the red light?
There are two different places you may find a red light as a fault code. On the boiler itself or on a wireless room thermostat receiver.
Red light on boiler
A red light on the boiler is normally an indicator of a fault. The red light will not be just flashing by itself. The boiler will have some other way of indicating the type of fault such as:
- a display with letters or numbers showing the type of fault.
- several lights indicating different faults when they are illuminated.
- a combination of lights flashing in different sequences to show different fault codes.
It’s important to make a note of the sequence of flashes or the letters and numbers displayed. This information will be very important when you try to find the fault or when you report the fault to a heating engineer.
A very helpful hint is to take a video of the fault code or lights flashing instead of trying to remember the sequence. The sequences can be quite complicated and difficult to remember.
Once you know the sequence you need to find the fault code descriptions.
Fault codes are always found in the instruction manual of your boiler.
How to find my boiler fault codes
- Find the manufacturer of your boiler. This will be printed on the front cover, under any fold down flap or possibly on a label on the bottom of the boiler eg Vaillant, Worcester or Baxi
- Find the model name/number of the boiler eg Vaillant ecotec pro, Worcester Ri or Baxi Duotec.
- Go to the manufacturers’ website and find the section on support, advice or documentation. If you can’t find the right part of the website search for the manufacturer name, model name then installation instructions. That normally brings up the right information.
- Now search through for the Fault finding section. All the appropriate fault codes for your boiler will be listed in this section.
What do I do next?
Some problems can be cleared and solved without too much work. Things like running out of gas or low water pressure are simple for non gas safe engineers to repair.
More complicated problems need to be repaired by qualified heating engineers. When you call the engineer they will be very grateful for the fault code information before they arrive.
Red light on wireless thermostat
Why does the red light show on my thermostat?
The wireless thermostat will regularly communicate with the receiver just to make sure the connection is still there. If they attempt to communicate and there is no response the receiver will display a communication error. This is normally shown as a red light but can be other colours depending on the model.
A red light on the wireless thermostat is usually caused by one of three things:
- Battery problems
- Faulty thermostat or receiver.
- Loss of communication
All wireless room thermostats take batteries. They are normally found under a little hatch along the top, the bottom or on the side.
If you can’t find the batteries search online for the instructions of the thermostat.
If the display is completely blank then it is highly likely the batteries have run out. This is a particularly common problem at the end of summer when the heating hasn’t been used for months.
Loss of communication
The wireless thermostat and the receiver are always paired up when they are installed. This provides the link between the two and avoids confusion if other thermostats are installed nearby. If the thermostat hasn’t been used for a while they can lose their pairing causing a communication problem.
The solution to this problem is to reconnect the thermostat with its receiver.
Each brand has its own method of reconnecting which as always is found in the instruction booklet. You either have this booklet stashed away somewhere or it will be available online.
Faulty thermostat or receiver
Unfortunately, over time some electronic devices will develop faults. If you have changed the batteries and reconnected the two parts and it still doesn’t work you may have to replace the thermostat.
What to do next
There are strictly two types of boiler faults. Things you can fix yourself and things you need a gas-safe engineer to fix.
Resetting the boiler, topping up the pressure, defrosting condensate pipes and putting more credit on gas meters if you run out are all fine to do.
Anything that involves removing the cover of the boiler is not ok and must be left to a qualified gas engineer.
The most common faults with room thermostats are dead batteries or loss of communication.
Most thermostats take 2 AA batteries. Replace the batteries as soon as you see the battery reminder symbol on the screen. If the screen is completely blank change the batteries, it’s always worth a try.
If the thermostat won’t connect or is showing a signal symbol you will have to find the instructions to reconnect the receiver.
Read the installation instructions, re-pairing thermostats is normally pretty straightforward.
The instructions are available online from the manufacturers’ website. You can match the model to the most popular versions here if you don’t know the model.