A.O. Smith fault code XAC-XXXX
Fault code XAC-XXXX on an A.O. Smith water heater (including Twister) means: (Lockout) Air pressure switch fault - The switch is not closed when the fan is running during pre-purge: The tubes are damaged. Reset the appliance once. If the code comes back, a part is usually faulty. You can check the water pressure and settings yourself; leave work on gas-carrying parts to a certified gas engineer.
After a safety alert (gas, flue gas, combustion), reset no more than once and call in a certified gas engineer. If you smell gas, call your national gas emergency number or 112 immediately.
Cause
Fault code XAC-XXXX on an A.O. Smith water heater indicates: (Lockout) Air pressure switch fault - The switch is not closed when the fan is running during pre-purge: The tubes are damaged.
Applies to
A.O. Smith Twister, TWI 35-200, TWI 45-200.
Fault code XAC-XXXX on other A.O. Smith series
The same code does not mean the same thing on every series. Check the rating plate to see which series you have:
- XAC-XXXX on Twister, TWI 35-200, TWI 45-200: (Lockout) Air pressure switch fault - The switch is not closed when the fan is running during pre-purge: The wiring is damaged.
- XAC-XXXX on Twister, TWI 35-200, TWI 45-200: (Lockout) Air pressure switch fault - The switch is not closed when the fan is running during pre-purge: Air leak between the venturi and the air connection.
- XAC-XXXX on Twister, TWI 35-200: (Lockout) Air pressure switch fault - The switch is not closed when the fan is running during pre-purge - Insufficient pressure difference in the air pressure switch, caused by: - the air supply and flue gas discharge system - condensate drain fault - fouled burner - blocked heat exchanger.
- XAC-XXXX on Twister, TWI 35-200, TWI 45-200: (Lockout) Fan fault - The switch is closed when the fan is not running: Damaged wiring/closed circuit.
- XAC-XXXX on Twister, TWI 35-200, TWI 45-200: (Lockout) Fan fault - The switch is closed when the fan is not running: Air pressure switch defective.
- XAC-XXXX on Twister, TWI 45-200: (Lockout fault) Air pressure switch fault - The switch is not closed when the fan is running during pre-purge - Insufficient pressure difference in the air pressure switch, caused by: - the air supply and flue gas discharge system - condensate drain fault - dirty burner - blocked heat exchanger.
Matching parts
A.O. Smith parts are available from Instalpunt; shipping to EU countries from €12.95 (€16.95 for more distant countries), usually 3–5 working days.
For fault code XAC-XXXX, the part involved is usually in the category: fan.
This message does not point directly to one faulty part. These are the parts that most often fit this appliance:
- A.O. Smith air pressure switch Twister 45-190 € 47.04
- A.O. Smith fuse 5x20 2AT 250V € 15.68
- A.O. Smith 3-way fused terminal block € 26.14
Fix it yourself or call an engineer?
Always consult the manual for your appliance and work safely. If in doubt or if the fault comes back, call in a qualified professional. A question about a part? Write to us at info@instalpunt.nl.
Frequently asked questions
What does A.O. Smith water heater fault code XAC-XXXX mean?
(Lockout) Air pressure switch fault - The switch is not closed when the fan is running during pre-purge: The tubes are damaged.
How do I fix fault code XAC-XXXX on an A.O. Smith water heater?
First check the cause described above. Then restart the appliance using the reset button. If the message comes back, a part usually needs replacing or the fault needs to be repaired by a qualified professional.
Which parts do I need for A.O. Smith fault code XAC-XXXX?
That depends on the exact cause. In the A.O. Smith parts overview at Instalpunt you will find the current price and stock for each part.
Can I fix fault code XAC-XXXX myself?
You can reset the appliance and check things like the water pressure or settings yourself. Work on gas-carrying parts must be left to a certified gas engineer.
All A.O. Smith water heater faults and codes at a glance →