Baxi 600 Combi Problems — Fault Codes & Fixes
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The Baxi 600 is a dependable workhorse found in thousands of UK homes, from new-build flats to social housing, but like any combi boiler it can develop faults that leave you without heating or hot water. Most problems are straightforward to diagnose using the boiler's fault codes — a clever system that tells you exactly what's gone wrong, whether it's low pressure, an ignition fault, or a fan issue. The good news is that many Baxi 600 faults can be resolved quickly with basic checks you can do yourself, though some will need a qualified Gas Safe engineer to put right safely. This guide walks through the most common fault codes, what they mean, and whether you can fix it or need professional help.
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Most likely cause & what to check
The Baxi 600 (24kW and 28kW combi) is a popular budget boiler widely used in social housing and new-build properties. It is compact and generally reliable, though some batches have had reported PCB reliability issues. Full fault code guides at baxi.co.uk/support or call 0344 871 1525.
Fault code E119 (low system pressure): most common fault on the Baxi 600. Check the pressure gauge — it should read between 1 and 1.5 bar cold. Repressurise via the filling loop (two small valves under the boiler — the Baxi 600 uses a keyway-type filling loop on some variants). Fill to 1.2 bar, close both valves, press reset. If pressure drops again within a few days, there is a leak.
Fault code E133 (no ignition detected): the boiler has failed to light. Reset once. Check gas is working at other appliances. If E133 persists, an ignition electrode, ignition lead, or gas valve fault is likely — a Gas Safe engineer is needed.
Fault code E168 (fan fault): the flue fan is responsible for safely removing combustion gases. If E168 appears, do not reset repeatedly — call a Gas Safe engineer to inspect the fan and flue.
Boiler repeatedly locking out (showing lock padlock symbol): if the Baxi 600 goes to lockout frequently and different fault codes appear each time, a PCB (printed circuit board) fault may be the cause. PCB failure is more common on the 600 range than on premium boilers — a Gas Safe engineer can test the board.
Baxi 600 warranty is typically 2 years parts, 1 year labour — shorter than premium brands. For out-of-warranty repairs, parts are widely available from plumbers' merchants. Any Gas Safe engineer can work on the 600 range.
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Frequently asked questions
What should my boiler pressure reading be, and why does it keep dropping?
Your Baxi 600 should sit at 1–1.5 bar when cold; if it's lower, it'll trigger an E119 fault code and the boiler won't fire. A pressure drop over several days usually points to a slow leak in the system — check pipes under the boiler first, but a Gas Safe engineer can locate hidden leaks in the network or heating loop.
My boiler keeps showing E133 and won't ignite — is it dangerous to keep resetting it?
Repeated resets won't harm the boiler, but they won't fix the problem either if it's a faulty ignition electrode or gas valve. Always check that gas is reaching other appliances (your cooker or fire) first; if they work fine but the boiler won't light, book a Gas Safe engineer rather than keep resetting.
Is the Baxi 600 reliable, and does it have known issues?
The 600 is generally solid and cost-effective, but some production batches have had PCB (circuit board) issues that cause repeated lockouts and random fault codes. If your boiler is locking out frequently with different codes each time, a PCB fault is likely and you'll need an engineer to diagnose and replace the board if necessary.
My warranty has expired — will any plumber fix the Baxi 600, and are parts expensive?
Yes, any Gas Safe registered engineer can work on the 600 range; it's a common model so parts are readily available from plumbers' merchants and competitively priced. Out-of-warranty repairs are often affordable compared to premium boilers, and labour costs won't be inflated because the 600 is straightforward to service and repair.