Occurs when Air Pressure connection is open
The AIR PRESSURE Switch Open error code on Weil-Mclain boilers indicates occurs when air pressure connection is open.
Weil-Mclain AIR PRESSURE Switch Open means: occurs when air pressure connection is open. The usual cause is occurs when the high flue pressure switch is open. You can safely reset the boiler once — if AIR PRESSURE Switch Open returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does AIR PRESSURE Switch Open Mean
The AIR PRESSURE Switch Open code is shown by the boiler’s control board when it detects occurs when air pressure connection is open. 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 AIR PRESSURE Switch Open and the boiler stops until the fault is cleared |
Common Causes
Causes documented in the Weil-Mclain service literature published by weil-mclain.com, cross-checked against the manufacturer’s fault-code table.
| Cause |
|---|
| Occurs when the High Flue Pressure switch is open |
Safety Warning
AIR PRESSURE Switch Open 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
Check boiler size selected in control against boiler rating label. Correct if necessary to select the proper boiler size
Check exhaust and intake pipe for restrictions or blockage
Check condensate drain for blockage. If condensate is unable to drain out of the boiler it can begin to block the flow of exhaust gases. Clean the condensate collection area of the base and condensate trap. Refill trap with fresh water
Check the P7 connection as seen on Figure 52, page 60 & Figure 53, page 62. Check the connections on the pressure switch
Check the P7 connection as seen on Figures 52, page 48
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 AIR PRESSURE Switch Open:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Weil-Mclain models | — | Possible |
Frequently Asked Questions
Check boiler size selected in control against boiler rating label. Correct if necessary to select the proper boiler size. According to the technical documentation, this is the first check on the list for AIR PRESSURE Switch Open.
AIR PRESSURE Switch Open is not classified as a high-severity fault, so the boiler can be reset once. If AIR PRESSURE Switch Open comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.