Rheem Tankless Error Code 76: Display or Remote Controller Communication Failure (Meaning, Causes, Fixes)

What the code means

Rheem's High and Super High Efficiency Tankless Troubleshooting Manual (AP21822) defines 76 as a built-in display (or remote controller) to water heater communication failure: if the built-in controller or the remote controller is not communicating with the control board, the heater shows 76 on that controller. The manual's check method is the same idea for both: turn power off, remove and reinsert the control board connector and the molex plug for the built-in display (or for the remote controller), visually inspect the wiring for loose or damaged connections, then turn power on and run the unit. If 76 doesn't come back, the unit simply had a loose connection. If it does, a technician measures the DC signal voltage at the control board connector. A reading outside Rheem's range points to the connector or the control board; a normal reading means the built-in display, or the remote controller, is the part to replace. Rheem's older Technical Service Bulletin for RTG 74 tankless fault codes lists 76 as Communication Fault with Remote Control, with remedies of checking the remote control wiring for loose or damaged connections, bypassing the remote cable by connecting the remote directly to the remote control terminals on the circuit board (and replacing the cable if it's faulty), and finally replacing the remote control.

Likely causes

• A loose or partly unplugged connector between the control board and the built-in display, which Rheem's check method treats as the first and most common fix
• Damaged, pinched or corroded remote controller wiring, or a bad connection at the remote's terminals
• A faulty remote control cable on older RTG models, which Rheem's bulletin says to test by connecting the remote directly at the circuit board
• A failed built-in display or remote controller
• A failed control board, when the communication voltage at the board connector is out of Rheem's range

Safe DIY checks

1. Write down the code, your model number from the rating plate, and whether the code shows on the heater's built-in display or on a wall-mounted remote controller.
2. Turn the heater off at its power switch or unplug it, wait a minute, and turn it back on. A one-time glitch may clear; if 76 returns right away, keep going.
3. If you have a wall-mounted remote, check the thin remote cable along its run for anything that pinched, cut or chewed it, and make sure the wires at the remote's own terminals are snug.
4. If a remote was recently added, moved or rewired, that work is the first suspect; have whoever did it recheck the connections.
5. Don't open the heater's front cover to reseat board connectors unless you're comfortable working around live 120-volt wiring with the power off and verified off. Otherwise leave the connector check to a pro.
6. If 76 keeps coming back after a power cycle and a wiring check, call for service with the code and model number.

Parts that commonly fix it

Always match the part number to your exact model.

Related codes

• 12 Rheem Tankless Water Heater 12
• 13 Rheem Tankless Water Heater 13
• 14 Rheem Tankless Water Heater 14
• 29 Rheem Tankless Water Heater 29
• 45 Rheem Tankless Water Heater 45

All Rheem codes →

Sources

1. Rheem High and Super High Efficiency Tankless Water Heater Troubleshooting Manual AP21822, pages 56-58 (76 Error Code: Built-in display or remote controller to water heater communication failure; reseat connector and display or remote molex, inspect wiring, DC voltage check, replace control board or the display or remote controller)
2. Rheem Technical Service Bulletin, RTG 74 Tankless Fault Codes (Indoor, Outdoor and Heavy Duty models): 76 Communication Fault with Remote Control (check wiring, bypass remote cable at the PCB, replace cable or remote control)