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Error code reference

A.O. Smith Water Heater Error Code 741

Remote controller communication failure

A.O. Smith codesA.O. Smith water heater codes

Remote controller communication failure — miscommunication between the temperature remote controller and the water heater.

First step from the service manual

Check that all wiring is properly connected to the remote.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
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What 741 means on a A.O. Smith water heater

Error code 741 on an A.O. Smith water heater indicates a communication failure between the remote temperature controller and the water heater unit. This code is triggered when the control board detects that the data signal being transmitted between the remote controller and the heater has been interrupted, corrupted, or lost entirely. The remote controller communicates with the water heater through a wired connection, and any disruption in that signal path will cause the unit to flag this fault condition.

The most common source of this error is a wiring problem at the remote controller terminals. Loose, corroded, or improperly seated wires can interrupt the communication signal without any visible damage to the wire itself. The connection points at both the remote controller end and the water heater terminal block should be inspected closely. Wires that were not fully seated during installation or that have worked loose over time are frequent culprits.

Beyond loose connections, a damaged communication cable, a faulty remote controller, or a failed control board can also produce this fault. Physical damage to the wire run between the unit and the remote, such as a pinched or cut cable, will sever the data path. If wiring inspections and reseating connections do not resolve the error, the remote controller itself may have an internal fault and require replacement. In some cases, the control board on the water heater may be unable to send or receive the communication signal properly.

Source: manufacturer service documentation.

Common causes of 741

  1. 01

    Loose or disconnected wiring at the remote controller

    Wiring / connection

    Wires that are not fully secured at the remote controller terminals will interrupt the communication signal. Check all terminal connections at the remote and reseat any that appear loose or partially inserted.

  2. 02

    Loose wiring at the water heater terminal block

    Wiring / connection

    The communication cable also connects to a terminal block on the water heater itself. Inspect those terminals for loose, corroded, or improperly connected wires, which can disrupt the signal just as easily as a problem at the remote end.

  3. 03

    Damaged communication cable

    Part replacement

    Physical damage along the wire run, such as a pinched, cut, or severely kinked cable, will break the data path between the remote and the heater. Inspect the full length of the cable for any visible damage.

  4. 04

    Faulty remote controller

    Part replacement

    If all wiring checks out and connections are secure, the remote controller unit itself may have developed an internal failure. A defective remote will need to be replaced to restore communication.

  5. 05

    Failed control board on the water heater

    Part replacement

    In less common cases, the water heater's control board may be unable to properly send or receive the communication signal. This is typically suspected only after wiring and the remote controller have been ruled out.

See the test procedure for each cause

Frequently asked questions about 741

What does 741 mean on a A.O. Smith water_heater?
Error code 741 means the water heater has detected a communication failure with the remote temperature controller. The unit is not able to properly exchange data with the remote over the wired connection between the two devices. This is most commonly caused by loose or improperly connected wiring at either the remote or the heater's terminal block.
How do I fix error code 741 on my A.O. Smith water heater?
Start by checking that all wiring connections are fully and properly seated at the remote controller terminals and at the terminal block on the water heater itself. If connections look secure, inspect the entire length of the communication cable for physical damage such as cuts or pinching. If wiring is intact and properly connected, the remote controller unit may need to be replaced. If replacing the remote does not resolve the fault, the water heater's control board should be evaluated.
Is error code 741 on an A.O. Smith water heater a safety concern?
Error code 741 is a communication fault rather than a combustion or temperature safety issue. However, if the remote controller is used to manage water temperature, losing that control link means you may not be able to adjust settings remotely. You should address the fault promptly to restore full control of the unit, but the error itself does not indicate an immediate safety hazard.
Will resetting my A.O. Smith water heater clear error code 741?
A reset may temporarily clear the code, but the error will return if the underlying wiring or component issue has not been resolved. The communication fault is detected continuously, so as long as the signal path between the remote and the heater remains broken or unstable, the 741 code will reappear. Fix the root cause before relying on a reset.
How much does it cost to repair error code 741 on an A.O. Smith water heater?
If the fix is simply reseating loose wires, there is no parts cost involved. Replacing a damaged communication cable is typically a low-cost repair, generally in the range of $10 to $40 for the cable depending on length. A replacement remote controller can range from $50 to $150 or more depending on the model. If the control board on the water heater requires replacement, costs can range from $150 to $400 or higher, not including labor.

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