Blower is outside of minimum or maximum speed for 10 seconds
The Blower Fault 3 error code on Weil-Mclain boilers indicates blower is outside of minimum or maximum speed for 10 seconds.
Weil-Mclain Blower Fault 3 means: blower is outside of minimum or maximum speed for 10 seconds. On this component the documented failure modes are blower is outside of minimum or maximum speed for 10 seconds, fan blocked, worn or its speed signal wrong or wiring, connector or harness of the fan damaged or loose. You can safely reset the boiler once — if Blower Fault 3 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does Blower Fault 3 Mean
The Blower Fault 3 code is shown by the boiler’s control board when it detects blower is outside of minimum or maximum speed for 10 seconds. 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 Blower Fault 3 and the boiler stops until the fault is cleared |
Common Causes
The first cause below is the one the Weil-Mclain service literature publishes for this code (source: weil-mclain.com). The others are the failure modes documented for the same component on other boilers, confirmed by 13 different manufacturers.
| Cause |
|---|
| Blower is outside of minimum or maximum speed for 10 seconds |
| Fan blocked, worn or its speed signal wrong |
| Wiring, connector or harness of the fan damaged or loose |
| The fan has failed — short circuit or open circuit |
Safety Warning
Blower Fault 3 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
One hour automatic reset
Check the fan turns freely, then check its connector, wiring and speed signal; replace the fan if the bearings are worn or the signal is absent.
Unplug and re-seat the connector of the fan, then check the harness for chafing, corroded pins and breaks in continuity.
Measure the resistance of the fan with a multimeter and compare it against the manufacturer’s resistance-versus-temperature table; replace it if it is open circuit, short circuit or out of range.
Refer to the Weil-Mclain service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Weil-Mclain models that can display fault code Blower Fault 3:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Weil-Mclain models | — | Possible |
Frequently Asked Questions
One hour automatic reset. According to the technical documentation, this is the first check on the list for Blower Fault 3.
Blower Fault 3 is not classified as a high-severity fault, so the boiler can be reset once. If Blower Fault 3 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.