Baxi Boiler 166 Fault Code
The Baxi fault code 166 air pressure switch Q & A or require an engineer for an emergency boiler repair.
The Baxi Boiler Fault Code 166 Error Common Q & A
Just below, we have a list of common questions relating to the 166 fault code on the Baxi boiler.
- What does the 166 fault code mean on my Baxi boiler?
- What does the pressure switch on my boiler do?
- Does a lockout mean my boiler is broken?
- What faults can occur with a pressure switch?
- How will I know if it’s bad wiring causing the 166 fault code on my Baxi boiler?
- How is water damage caused on a boiler?
- How will kinked hoses cause the 166 fault code to be displayed?
- What parts in a boiler can affect the pressure switch’s operation?
- How can the fan cause problems with the pressure switch?
- How can the flue cause issues with the pressure switch?
- If the air pressure switch is faulty, what’s the cost to replace it?
What does the 166 fault code mean on my Baxi boiler?
The 166 fault code on Baxi boiler relates to an air pressure switch fault.
There’s either an external component not allowing the switch to work correctly, or the switch itself is faulty.
What does the pressure switch on my boiler do?
The air pressure switch on your Baxi boiler monitors the flow and pressure of air in your boiler.
The focus here is on the draught in the flue. The flue (the large white pipe on the side of your property) takes waste gases from inside the boiler, to the outside of your property.
It’s only able to do this, thanks to the fan. The fan creates a draught, which changes the air pressure in the flue. This draught helps to direct the gases out of the boiler, and through the flue.
What the air pressure switch is monitoring, is this draught. If there is no air pressure change during the ignition sequence, that means the fan isn’t operational. If the fan isn’t operational, the waste gases won’t be taken from your property.
That’s dangerous, and it’s this exact danger that the pressure switch is looking for. When it sees no change in pressure, it feeds back a signal to the PCB (your boiler’s circuit board), and the boiler will then lock out.
Does a lockout mean my boiler is broken?
The boiler lockout from the sequence above doesn’t mean your boiler is broken completely. What it means is there is an issue with air pressure, which could relate to flue gases not escaping the boiler.
This is a dangerous fault. The boiler locks out to protect the people in your property.
The problem needs to be fixed, and the boiler reset. If the problem is fixed, the 166 fault code should clear when the boiler fires up again.
However, don’t keep resetting the boiler to clear the fault. If you manage to fool the boiler into thinking the problem is fixed with a reset, you’ll be filling up your home with dangerous gases.
Get help from a Gas Safe engineer.
What faults can occur with a pressure switch?
There are a range of faults that can occur with the pressure switch, including:
- Bad wiring too/from the PCB
- Water damage
- Kinked hoses
How will I know if it’s bad wiring causing the 166 fault code on my Baxi boiler?
You should always have a Gas Safe boiler engineer fix your boiler for you, it’s unsafe to work on gas appliances if you’re not trained.
Issues with wiring become obvious with a visual inspection. Typically, we find that bad wiring comes in the form of loose connections. These connections have been worked loose due to years of internal boiler vibrations.
When wiring becomes loose (but is still partially connected) it can send intermittent signals to and from the PCB.
And, that leads to intermittent operation of your boiler. So, you might have noticed things such as:
- The boiler cycling on and off
- Your boiler cycling off before hot water/heating is up to temperature
- The display panel on your boiler flickers, or only works on occasion
How is water damage caused on a boiler?
If you’ve noticed that the pressure on your boiler is dropping (there’s a pressure gauge on the front, or underneath the boiler’s casing), that’s a sign of a leak.
Not all leaks are inside the boiler, but if you’re having electrical problems, there’s a good chance that’s the case.
A common part that leaks in older boilers is the heating pump. The leak can start due to bad installation, or even blown seals.
When it starts, it only gets worse over time. The difficult part isn’t fixing the leak (replacing pump seals, is relatively straight forward). The problem is the damage it causes by the time the it’s found and fixed.
Any moisture on electronic components (including the air pressure switch) is going to cause them to malfunction.
How will kinked hoses cause the 166 fault code to be displayed?
The pressure switch monitors air pressure via hoses. If these are, or become kinked, the air pressure readings will be incorrect.
This will cause the switch to give the wrong signals to the PCB. That means the boiler could lockout, as the pressure switch thinks the air pressure is incorrect, even though it isn’t.
Unless this is a new installation, it’s likely that the hoses have been kinked by a recent repair. If the hoses have been moved slightly whilst trying to repair another part, even a small kink will have affected the air pressure.
The boiler casing needs to be removed (by a Gas Safe engineer) and the hoses need to be routed so they’re unobstructed by any other internal boiler parts.
What parts in a boiler can affect the pressure switch’s operation?
Although this fault code relates directly to a switch fault, other issues can’t be ruled out. Fault codes on boilers are usually fairly accurate, but not 100% accurate.
Instead of a switch fault, this could be a problem with something that’s connected to the switch, including:
- The boiler’s fan
- The flue
How can the fan cause problems with the pressure switch?
If you’ve noticed other boiler fault codes being displayed on your Baxi boiler recently, there’s a good chance they relate to the fan.
If the fan isn’t operational, the pressure switch will lock out the boiler.
The fan could have water damage to the electronics and be sending incorrect signals to the PCB (for instance, that it’s not running, even when it is).
Unless an electronic fault can be blamed, this is usually due to partially seized fan bearings, or a seized motor. When a fan has deteriorated to this point, a replacement is usually needed.
How can the flue cause issues with the pressure switch?
Like the fan, the flue is integrated into the operation of the pressure switch. A problem with any one of these three parts will cause the boiler to lock out.
If you’ve noticed any other fault codes on your Baxi boiler linked to an “air fault”, there’s a good chance your flue is to blame.
Typically, this will only be an issue with vertical flues, that go through your roof (a lot of boilers use a horizontal flue – through the wall).
These flues should be fitted with a flue guard. These look a little like a bird cage and they stop debris dropping into the flue.
If one has not been fitted, there’s a good chance debris has made its way into the flue. The flue needs to be cleared, and a cage fitted.
If the air pressure switch is faulty, what’s the cost to replace it?
If the wiring, connections, or switch itself can’t be repaired, you’ll need a replacement.
A replacement should cost under £300.
Around £100 of this will be allocated for parts, and approximately £200 will be the cost for labour.
Other Baxi boiler issues
For more boiler issues regarding the Baxi Boiler then please visit the Baxi Boiler Problems And Cures page.