AO Smith 741: Remote Controller Miscommunication
If your wall-mounted temperature remote suddenly goes blank, shows an odd reading, or throws code 741, the unit itself may still be running fine — this is a communication problem between the remote and the control board, not necessarily a combustion issue.
Applies to: AO Smith tankless/condensing water heaters with a wall-mounted remote temperature controller
What it means
Remote Controller Miscommunication — the wired remote isn't communicating properly with the unit's control board. Because the remote is really just a convenience interface layered on top of the water heater's own logic, this is one of the few AO Smith codes where the unit can often keep heating water on a default setting even while the remote itself is offline.
Most common causes
- Wrong model of remote controller installed
- Loose or damaged wiring between the remote and the unit
- Failed remote control or control board
What you can safely check yourself
- Check the wiring connections between the remote control and the unit for looseness or damage
- Confirm you have the correct remote model specified for your unit
When to call a professional
Connections look fine and the correct remote is installed, but the code persists — remote or board replacement is likely needed.
If wiring and remote-model checks don't clear it, have a licensed HVAC technician confirm whether the remote or the control board is at fault before replacing either part.
What the fix costs
A replacement wired remote is typically a modest part cost plus a service call, often landing in the $150–$300 range once labor is included — well below the $250–$600 that HomeGuide and Angi cite for a full control board swap, which is why it's worth confirming which component actually failed before paying for either. If the unit is still heating water at a default temperature while you sort this out, there's usually no urgency to the repair itself.
Related codes
All AO Smith codes
Every AO Smith water heater fault code — the full list on one page. Since the remote controls the temperature setting, a communication fault here can leave the unit running at a default temperature — see water not hot enough or runs lukewarm if that's what you're noticing.
Sources
- AO Smith tankless water heater error code guide (manufacturer documentation)