Combustion pressure and Flame OFF
The 157 error code on Slant-Fin boilers indicates combustion pressure and flame off.
Slant-Fin 157 means: combustion pressure and flame off. On this component the documented failure modes are wiring, connector or harness of the false flame damaged or loose, ignition or detection electrode dirty, worn or out of position or faulty gas valve, or its wiring and connector. You can safely reset the boiler once — if 157 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does 157 Mean
The 157 code is shown by the boiler’s control board when it detects combustion pressure and flame off. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows 157 and the boiler stops until the fault is cleared |
Common Causes
The manufacturer does not publish a cause list for this specific code. The causes below are the failure modes documented for the same component on other boilers, confirmed by the service literature of 6 different manufacturers.
| Cause |
|---|
| Wiring, connector or harness of the false flame damaged or loose |
| Ignition or detection electrode dirty, worn or out of position |
| Faulty gas valve, or its wiring and connector |
Safety Warning
157 involves electrical or pressure-related components. Do not attempt repairs without proper qualifications. Ensure the boiler is electrically isolated before any inspection. If you notice water leaks, unusual sounds, or pressure anomalies, contact a qualified heating engineer immediately.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
How to Fix It
Unplug and re-seat the connector of the false flame, then check the harness for chafing, corroded pins and breaks in continuity.
Inspect the ignition and detection electrode: clean off any deposits, check the gap and position against the manual, and replace it if it is worn.
Check the gas valve connector and wiring for continuity, then test the valve coil resistance against the manual; replace the valve if it is out of range.
Refer to the Slant-Fin service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Slant-Fin models that can display fault code 157:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Slant-Fin models | — | Possible |
Frequently Asked Questions
Unplug and re-seat the connector of the false flame, then check the harness for chafing, corroded pins and breaks in continuity. According to the technical documentation, this is the first check on the list for 157.
157 is not classified as a high-severity fault, so the boiler can be reset once. If 157 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.