A.O. Smith fault code XC9-XXXX
Fault code XC9-XXXX on an A.O. Smith water heater (including Twister) means: (Lockout) Control fault - Hardware fault: Disconnect the selection knob. 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 XC9-XXXX on an A.O. Smith water heater indicates: (Lockout) Control fault - Hardware fault: Disconnect the selection knob.
Fixing fault code XC9-XXXX: step by step
- Switch the appliance off at the mains for 30 seconds (unplug it), then switch it back on.
- Is it about communication with the thermostat? Then check the thermostat connection and wiring.
- Reset the appliance once. If the code comes straight back, do not keep resetting it.
- If the code comes back, the PCB or burner control unit is probably faulty. Have the appliance read out first to be sure.
Applies to
A.O. Smith Twister, TWI 35-200, TWI 45-200.
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.
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 € 48.93
- A.O. Smith fuse 5x20 2AT 250V € 16.31
- A.O. Smith 3-way fused terminal block € 27.18
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 XC9-XXXX mean?
(Lockout) Control fault - Hardware fault: Disconnect the selection knob.
How do I fix fault code XC9-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 XC9-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 XC9-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 →