Can I keep running the equipment with this fault active?

Generally no. Faults on Water heater units are emitted when a sensor, safety, or control circuit is outside its operating envelope. Running through an active fault risks compressor, heater, or control-board damage. Diagnose and clear the fault first.

What part is most commonly replaced for Rheem Tankless Water Heater Control Board Replacement Guide?

The most frequently replaced parts for Rheem Tankless Water Heater Control Board Replacement Guide are listed in the Parts Reference section of this guide with OEM part numbers and typical price ranges. Check the table for direct replacements.

Is Rheem Tankless Water Heater Control Board Replacement Guide a DIY repair or do I need a technician?

Sensor swaps, fan motor replacements, and condenser cleaning are typical DIY-level repairs. Anything involving refrigerant, gas, or high-voltage (>240V) work requires a licensed technician for both safety and code-compliance reasons.

Rheem Tankless Water Heater Control Board Replacement Guide

Q: What does Rheem Tankless Water Heater Control Board Replacement Guide mean?

Persistent error codes, ignition failures, no heating, or unresponsive controls mean your PCB is faulty. Replacing the control board restores normal operation after you rule out sensors and wiring.

Q: How do I fix Rheem Tankless Water Heater Control Board Replacement Guide?

Follow the step-by-step diagnosis below. The most likely fix is identified by checking power, sensor resistance, and control-board signals in order — using a multimeter and the part numbers documented in the parts reference table.

Rheem Tankless Water Heater Control Board Replacement Guide — What This Part Does

The control board (PCB or main board) is the electronic brain of your Rheem tankless water heater. It reads inputs from temperature sensors and the flame rod, controls the gas valve and igniter during startup, drives the fan and water valve, and displays error codes when something goes wrong. Most of the time, a board fault shows up as repeated error codes even after you’ve checked the physical components the board monitors.

Boards fail because of power surges, moisture intrusion, component wear, or corrosion on traces and connectors. Rheem’s troubleshooting workflow is to diagnose the displayed error code first and test field components like sensors, igniters, flame rods, and gas valves before replacing the PCB. A true board failure happens when all those parts check out but the unit still won’t ignite, won’t stay lit, or throws persistent codes like 11 (ignition failure), 12 (flame failure), 16 (overheating), or 80/81 (gas control issues).

Jump to Replacement Steps

Signs It Needs Replacing

Persistent error code 11 or 12 after checking igniter and flame rod The display shows ignition or flame failure codes even though you’ve confirmed the igniter glows, the flame rod is clean, and gas pressure is correct.
No ignition attempt when you open a hot tap The unit’s display powers on but the fan doesn’t spin, the igniter doesn’t glow, and you hear no relay clicks when you call for hot water.
Error code 16 (over-temperature) with clear vents and normal flow The heater trips on high-temp cutoff even though the vent is clear, the filter is clean, and water flow is adequate.
Unit cycles power or resets randomly during operation The display goes dark or reboots mid-cycle without any external power interruption or tripped breaker.
Remote controller or display is unresponsive or shows garbled text The remote display is blank, frozen, or shows random characters even after you’ve tested the cable and replaced the remote.
Gas valve doesn’t open even though all safety checks pass You’ve confirmed gas pressure, tested the gas valve solenoids, and checked the flame sensor, but the valve still won’t energize.

How to Replace It

Turn off electrical power to the water heater at the breaker or unplug the unit.
Close the cold-water inlet isolation valve and open a hot tap downstream to relieve pressure in the system.
Remove the front cover or access panel by unscrewing the fasteners.
Take a clear photo of all wire connections to the control board, labeling each harness if needed.
Disconnect all wire harnesses from the control board by gently pulling on the connectors, not the wires.
Remove the screws securing the control board to its mounting bracket or chassis.
Lift the old control board out of the unit.
Position the new control board on the mounting bracket and secure it with the original screws.
Reconnect all wire harnesses to the new board using your photo as a reference, pressing each connector firmly until it clicks.
Replace the front cover, open the cold-water inlet valve, turn electrical power back on, and observe the startup sequence for error codes.

The Part You Need

Part	Notes
Rheem tankless water heater control board / PCB / main board	Amazon \| Match the board part number printed on your old board or consult the model and serial number on the rating plate inside the front cover. Rheem tankless models use different boards by series (RTG, RTGH, RTEX, etc.), so cross-reference your exact model before ordering.

If this part is failing you may also see one of these codes:

When to Call a Pro

Gas-fired tankless heaters require proper combustion diagnostics, gas-pressure testing, and flame-rod voltage checks that are difficult without a multimeter and manometer. If you’re not confident reading wiring diagrams, testing sensors, or working around 120V or 240V power and natural-gas or propane lines, call a licensed plumber or gas technician. A pro can also verify that the new board is programmed correctly for your fuel type and venting configuration and can confirm that the root cause wasn’t a failed sensor or corroded connector that will damage the replacement board. For gas line, burner, or igniter work, or if you ever smell gas, stop and call a licensed technician.