E168 Error on Baxi Boiler? Comprehensive Fix Guide

The Baxi Error E168 is a diagnostic code indicating a non-specific electrical fault, typically involving the Printed Circuit Board (PCB) or an inconsistent external power supply. It occurs when the boiler’s “brain” detects a voltage abnormality or internal component failure that prevents it from verifying safe operating parameters, leading to a system lockout.

If you are seeing this code, you are likely dealing with a boiler that refuses to fire up, leaving you with cold radiators and an ice-cold shower. You might hear the boiler clicking as it attempts to ignite, only to fail and display the dreaded E168 digits. In some cases, the boiler might work sporadically—resetting itself before failing again an hour later. While electrical issues sound daunting, this guide will help you navigate the diagnostic process. Don’t worry; whether it’s a simple power reset or a board replacement, this is a solvable issue.

The Complete Solution

Step 1: Perform a Hard System Reset
Before opening the unit, attempt a “Hard Reset.” Turn the boiler’s selector switch to the ‘R’ (Reset) position and hold it for at least five seconds. If the error is caused by a temporary software hang or a one-time voltage spike, this may clear the fault. If the code persists, move to a power-cycle: turn off the fused spur switch (the power switch near the boiler), wait two minutes for the capacitors to fully discharge, and turn it back on.

Safety Warning: If you smell smoke or a “burning plastic” scent, do not attempt to reset; keep the power off.

Step 2: External Supply Audit
Using your digital multimeter set to AC Voltage (750V range), check the power at the fused spur. You are looking for a stable reading between 230V and 240V. If the reading fluctuates wildly (e.g., dropping to 210V or jumping to 255V), the issue is likely your home’s wiring or the local grid, not the boiler itself. Also, ensure the fuse in the spur is a 3-amp fuse; using a higher-rated fuse can allow surges to damage the PCB.

Step 3: Accessing the PCB and Visual Inspection
Ensure the power is completely isolated. Use your Phillips head screwdriver to remove the front outer casing of the Baxi. On most models, the control box will hinge down. Unclip the plastic PCB cover to reveal the green circuit board. Examine the board closely for “blown” capacitors (look for silver cylinders with bulging tops) or black soot marks near the transformers. If you see any physical damage or “leaking” fluid on the board, the PCB must be replaced.

Safety Warning: Never touch the PCB components while the power is on. Even with power off, some capacitors can hold a charge.

Step 4: Checking Terminal Tightness
Vibration from the pump and fan can occasionally loosen the wiring terminals. Using an insulated screwdriver, gently check that all wires entering the PCB (Live, Neutral, and Earth) are seated firmly. A loose Neutral wire is a notorious cause for the E168 code because it creates an unstable “floating” voltage. Ensure the ribbon cable connecting the display to the main board is also clicked firmly into place.

Step 5: Professional PCB Replacement (If Required)
If the wiring is secure and the power supply is stable, but the E168 code remains, the internal logic of the PCB has likely failed. Replacing a PCB involves transferring several wiring looms to a new board.

Note: In many jurisdictions, replacing internal boiler components must be done by a certified Gas Safe engineer, as the PCB controls the gas valve and safety timings.

What Triggers this Code?

Because E168 is a “generic” electrical fault, it acts as a catch-all for several underlying issues. Here is a deep dive into the most common triggers:

1. Voltage Spikes and “Dirty” Electricity: Modern Baxi boilers are essentially high-precision computers. If your local power grid experiences “surges” or “brownouts” (voltage drops), the PCB may detect that the incoming 230V signal is outside of the safe 10% tolerance. This triggers a lockout to prevent the sensitive microchips from frying. Long-term exposure to inconsistent voltage eventually degrades the board’s ability to process signals.

2. Component Degradation (PCB Aging): Inside the PCB are electrolytic capacitors and resistors. Over years of heat cycles (heating up while the boiler runs, cooling down when off), these components can leak or bulge. Specifically, the capacitors responsible for smoothing out the electrical current can fail, leading to “noisy” power inside the board that the software interprets as a fatal error.

3. Poor Grounding/Earth Connectivity: The boiler relies on a solid earth connection to bleed off static and reference its internal voltages. If the earthing wire in your home’s spur switch is loose or corroded, “stray” voltage can sit on the chassis. The PCB detects this imbalance and shuts down for safety reasons to prevent the risk of electric shock or short-circuiting.

4. External Electrical Interference: Occasionally, other high-draw appliances on the same circuit (like a faulty refrigerator compressor or a power shower) can “backfeed” electrical noise into the line. If the Baxi PCB isn’t properly shielded, this noise disrupts the communication between the sensors and the main processor.

Symptoms

The E168 error code rarely travels alone; it is usually accompanied by a specific set of physical behaviors from your Baxi unit. Understanding these signs can help differentiate between a minor glitch and a total hardware failure.

• Intermittent Lockout: The boiler may function perfectly for several days and then suddenly shut down with the E168 code flashing. This often points toward a “ghost” in the electrical supply or a failing capacitor on the PCB.
• The “Clicking” Loop: You might hear the internal relays clicking rapidly as the PCB tries to initialize the ignition sequence, only for the display to reset or throw the error code immediately.
• Lukewarm Water: If the error occurs during a mid-demand cycle, the boiler may throttle its output or cycle on and off so rapidly that the water never reaches the set temperature.
• Unresponsive Reset Button: In severe cases of PCB failure, pressing the reset button may have no effect, or the error may reappear within seconds of the system trying to reboot.

How to Prevent Error E168

Once you have cleared the error, take these steps to ensure the “brain” of your boiler remains healthy for years to come:

• Install a Dedicated Surge Protector: Since the E168 is often caused by grid instability, having a surge protection device (SPD) installed at your consumer unit (fuse box) can shield the boiler’s sensitive electronics from external voltage spikes.
• Annual Electrical Tightness Check: During your annual boiler service, ask the technician to specifically check the electrical terminations. Over time, the thermal expansion and contraction of copper wires can cause them to work loose from their terminals, leading to the arcing that triggers electrical codes.
• Keep the Environment Dry: Ensure there are no slow leaks from the auto-air vent or pump above the PCB housing. Moisture is the primary enemy of circuit boards; even a tiny amount of corrosion on the pins can trigger a communication fault.

Frequently Asked Questions

Can I still use the boiler if the E168 error is intermittent?
It is not recommended. While the boiler might work occasionally, an E168 indicates that the safety logic of the PCB is compromised. If the board cannot accurately monitor the flame or the fan speed due to an electrical fault, it could lead to an unsafe combustion scenario. It is best to keep the unit off until the fault is diagnosed.

Is the E168 error the same as an E160 error?
No. While both are electrical in nature, E160 specifically refers to a fan or fan-communication fault. E168 is a broader, more critical “system-wide” electrical failure. However, a failing fan can sometimes cause enough electrical noise to trigger an E168, making a thorough diagnosis essential.

Why did my E168 error turn into an E133 or E128?
This is common. As the PCB begins to fail, it may struggle to manage the gas valve (E133) or lose the flame signal (E128). If you see a rotation of different error codes, it almost certainly confirms that the PCB’s central processor is failing and can no longer process sensor data accurately.