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Error code reference

A.O. Smith Water Heater Error Code 761

Communication failure in a multiple heater Easy-Link setup

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

Communication failure in a multiple heater Easy-Link setup — master unit has lost communication with an indicated slave heater.

First step from the service manual

Verify that there is power to the unit that has lost communication.

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

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  • Wiring diagram references and connector pinouts from the OEM service manual
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What 761 means on a A.O. Smith water heater

Error code 761 on an A.O. Smith water heater indicates a communication failure within an Easy-Link multi-unit configuration. Easy-Link is A.O. Smith's system for networking multiple water heaters together, where one unit operates as the master controller and the remaining units operate as slaves. The master unit continuously monitors communication with each slave over the network. When that communication link is interrupted or lost entirely, the master generates error code 761 to identify which slave unit is no longer responding.

The most common technical causes of this fault fall into two categories: power loss at the slave unit or a failure in the communication wiring between units. If the indicated slave heater has lost power, whether due to a tripped breaker, a blown fuse, or a loose power connection, it will stop responding on the Easy-Link network and trigger this code at the master. Communication wiring faults such as broken conductors, loose terminal connections, corroded contacts, or miswired network cables can also interrupt the data signal between units even when both heaters are powered.

Diagnosing this code requires first confirming that the slave unit identified by the error is receiving power. After power is confirmed, the technician should inspect the physical Easy-Link communication wiring between the master and the affected slave, checking terminal connections at both ends for tightness and corrosion. If wiring is intact and connections are secure, the fault may point to a failed communication board or control module in either the master or slave unit.

Source: manufacturer service documentation.

Common causes of 761

  1. 01

    No power to the slave unit

    Wiring / connection

    A tripped circuit breaker, blown fuse, or disconnected power supply at the affected slave heater will cause it to go silent on the Easy-Link network. Check the slave unit's breaker and power connections as the first step.

  2. 02

    Loose or disconnected communication wiring

    Wiring / connection

    The Easy-Link network relies on physical wiring between units. A loose terminal, pulled connector, or accidental disconnection at either the master or slave end will break communication and trigger this fault.

  3. 03

    Corroded or damaged communication terminals

    Wiring / connection

    Corrosion or physical damage at the communication wiring terminals can degrade or fully interrupt the data signal between units. Inspect both ends of the network cable for oxidation, moisture intrusion, or bent terminals.

  4. 04

    Broken or shorted communication cable

    Part replacement

    A conductor inside the Easy-Link network cable may be broken, shorted, or pinched, preventing data from passing between the master and slave. Test or replace the cable if wiring and terminal inspections do not reveal the fault.

  5. 05

    Failed communication board or control module

    Part replacement

    If power and all wiring check out, a faulty control or communication board in the slave or master unit may be preventing proper network communication. This requires component-level diagnosis and likely board replacement.

See the test procedure for each cause

Frequently asked questions about 761

What does 761 mean on a A.O. Smith water_heater?
Error code 761 means the master water heater in an Easy-Link multi-unit setup has lost communication with one of the slave units in the network. The code identifies that a specific slave heater is no longer responding to the master controller. This can be caused by a power loss at the slave unit, a wiring fault, or a failed control component.
How do I fix error code 761 on my A.O. Smith water heater?
Start by verifying that the slave unit identified in the error is receiving power, including checking its circuit breaker and power connections. Next, inspect the Easy-Link communication wiring between the master and slave units, ensuring all terminals are tight, clean, and free of corrosion. If power and wiring are both confirmed good, the fault may require testing or replacing the communication board in the affected unit.
Will resetting the water heater clear error code 761?
A reset may temporarily clear the displayed error, but code 761 will return if the underlying communication fault is not resolved. The master unit will continue to detect that the slave is not responding until power is restored to the slave, wiring is repaired, or the failed component is replaced. A reset alone is not a fix for this fault.
Is error code 761 on an A.O. Smith water heater a safety concern?
Error 761 is a network communication fault rather than a direct safety hazard like a gas leak or pressure issue. However, if a slave unit is offline, your hot water system is operating below its intended capacity, which can affect supply to the building. The issue should be diagnosed and corrected promptly to restore full system operation.
How much does it cost to repair error code 761 on an A.O. Smith water heater?
If the fix is as simple as resetting a tripped breaker or tightening a loose wire connection, there may be little to no parts cost involved. If the communication cable needs replacement, parts costs are typically modest, in the range of a few dollars to around fifty dollars depending on length and type. A failed control or communication board is the most expensive scenario, with parts and labor potentially ranging from a few hundred dollars upward depending on the model and service rates in your area.

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