Symptom guide
Water heater error codes and flashing lights
Photograph the full code or flash pattern and find the exact model. Code meanings differ by brand, product family, and control generation.
Safety first: Do not bypass a sensor or safety switch to clear a code. A recurring lockout, gas odor, wet control, or overheating condition needs professional diagnosis.
Start here
Identify the unit before following a procedure
Photograph the rating plate, control or display, and the exact symptom. Model generations can use different controls and code meanings even when the brand name is the same.
- Choose the heater typeGas tank, electric tank, tankless, heat pump, indirect, or RV.
- Record the exact clueCode, flash count, leak location, sound, or timing.
- Use the closest guideConfirm every model-specific step against the label or manual.
Gas
6 guidesGas Valve Electronic Fault Detected
Electronic fault detected on a Bradford White ICON or Honeywell gas control is a valve electronics lockout. What the LED count means.
GasGas Water Heater Error Codes
Gas water heater codes are model-specific. Photograph the light or display, check only safe basics, and hire a licensed pro for repeats.
RheemRheem Blue Light Flashing 7 Times
Seven flashes on a Rheem, Ruud, or Richmond gas control indicates a lockout, often FVIR related. What it means and why it must not be bypassed.
RheemRheem Failed Ignition Lockout
A Rheem failed-ignition lockout means spark or glow didn't produce proven flame. How to read the LED or code and when a reset is appropriate.
RheemRheem Red Light Flashing 9 Times
Nine red flashes on a Rheem, Ruud, or Richmond gas control is a lockout, usually the chamber temperature sensor. What it means and next steps.
GasWater Heater Blinking Blue Light
A blinking blue light is usually the status LED on a Rheem, Ruud, or Richmond gas control. How to count the flashes and what the codes mean.
Electric
11 guidesAlpha Water Heater Red Light Blinking
Record the Alpha model and exact red-light pattern. Keep electrical covers closed and use model-specific instructions to interpret a fault.
A. O. SmithAO Smith E02 Code: High-Limit Trip
E02 on an A. O. Smith Energy Smart electric tank is a high-limit (ECO) trip. Why it happens, when one reset is reasonable, and when it isn't.
A. O. SmithAO Smith E55 Code: Leak Detected
E55 on an A. O. Smith Energy Smart tank means the leak sensor found water. Shut off power, find the wet part, and learn when the tank is done.
A. O. SmithAO Smith Hybrid Problems: Codes
A. O. Smith Voltex hybrid not heating? Common causes are a dirty filter, vacation mode, an element or ECO fault, a compressor code, or a leak.
EcoSmartEcoSmart Water Heater Troubleshooting
An EcoSmart tankless that is cold needs power, flow, error, or element checks. Photograph the display.
ElectricEnergy Smart Water Heater Troubleshooting
Energy Smart electric tank not heating? Causes include power loss, E01 dry fire, E02 high limit, element codes, or a module fault.
RheemRheem A108 Error: Condensate Blocked
Rheem hybrid A108 means the condensate sensor is wet or the drain is blocked. How to clear the drain safely and when a repeat code needs a pro.
RheemRheem Heat Pump Water Heater Problems
A Rheem hybrid not heating may have a dirty filter, vacation mode, an EcoNet code, a tripped ECO, a failed element, or a compressor lockout.
SeiscoSeisco Tankless Water Heater Troubleshooting
A Seisco tankless not heating usually has a missing 240 V leg, air in the chamber, a high-limit trip (122), or a leak detect code (126).
SioGreenSioGreen Tankless Water Heater Problems
Identify the SioGreen model, distinguish power and flow symptoms, and check heating demand without opening the cabinet or guessing error codes.
StateState Hybrid Water Heater ECC Code
ECC on a State hybrid water heater means the heat pump compressor isn't working. Backup elements may still heat. What to check and when to call.
Tankless
32 guidesAirthereal Tankless Troubleshooting
An Airthereal electric tankless running cold usually means no 240 V, low flow, a clogged inlet screen, or an E1–E4 code. What each code means.
A. O. SmithAO Smith Tankless Reset Button
Most A. O. Smith tankless units reset by cycling 120 V power, not a hidden button. When one reset is safe, and when a code or gas smell means stop.
A. O. SmithAO Smith Tankless Water Heater Troubleshooting
An AO Smith tankless that is cold needs a code, flow, power, gas, or vent check. Photograph the display.
A. O. SmithAO Smith Tankless With No Hot Water
An A. O. Smith tankless with no hot water usually has no 120 V, no flow signal, a lockout code, or no gas. Read the display before resetting.
AquahAquah Water Heater Troubleshooting
An Aquah tankless that stays cold usually has a power, flow, LP, clogged screen, or E-code problem. Safe checks for electric and propane units.
BaxiBaxi Tankless Troubleshooting: Codes & Lockouts
Baxi combi cold showers often trace to ignition (E133), low pressure (E118/E119), circulation, fan, diverter, or a scaled plate exchanger.
CampluxCamplux Water Heater Troubleshooting
Camplux tankless running cold? Common causes are empty LP, dead batteries, low flow, a tripped ODS, a clogged inlet, or an E1/E2 code.
NavienNavien Dead After a Power Outage
A Navien that won't heat after a power outage may have a tripped GFCI, a display set to Off, a lockout code, or freeze damage. What to check.
NavienNavien E003: Ignition Failure Lockout
Navien E003 means ignition failure: the unit tried to light and never proved flame. Common causes, a safe reset, and when to call a pro.
NavienNavien Error 598-00: RTC / Display Fault
Navien error 598-00 is a real-time clock fault on the front display board, not a heating failure. What to try and when the display needs replacing.
NavienNavien Water Heater Error 773-00
Navien 773-00 points to a model-specific control or communication fault. Photograph the display, power-cycle once.
NoritzNoritz Code 11: Ignition Failure
Noritz code 11 means ignition failure: the unit tried to light but never proved flame. Common causes, a safe reset, and when to call a pro.
NoritzNoritz Code 12: Flame Failure
Noritz code 12 means flame failure: the burner lit, then lost flame. Common causes like gas supply and venting, and when repeats need a pro.
NoritzNoritz Code 29: Neutralizer Lockout
Noritz code 29 means the condensate neutralizer cartridge needs service. What it means, how it's cleared, and when a repeat code needs a pro.
NoritzNoritz Tankless Water Heater Not Working
A Noritz tankless that won't heat usually has a power, flow, lockout, freeze, or gas problem. Read the code first, then follow the checks.
NoritzNoritz Tankless With No Hot Water
A Noritz with no hot water usually has no 120 V, no flow signal, a lockout code, or a gas or ignition fault. Read the display first.
QuietsideQuietSide Tankless Water Heater Problems
QuietSide tankless and combi units fail on ignition, fan or pressure switch, low loop water, or a stuck 3-way valve. What the codes mean.
RheemRheem Code 11: Ignition Failure
Code 11 on a Rheem tankless means ignition failure: the unit never proved flame. Common causes, one safe reset, and when to call a technician.
RheemRheem Tankless Error Code 12: Flame Loss
Rheem tankless code 12 means the burner lit and then lost flame. Common causes like gas supply and venting, a safe reset, and when to stop.
RheemRheem Tankless Water Heater Flashing 11
Rheem tankless code 11 means ignition failure: no flame was proven. Common causes like a closed gas cock or dirty flame rod, and one safe reset.
RheemRheem Tankless Water Heater Troubleshooting
A Rheem tankless that won't heat usually has a power, flow, lockout, freeze, or gas problem. What codes 11, 12, and 14 mean.
RinnaiRinnai Beeping With Code 17
Rinnai code 17 on SENSEI units means a venturi blockage in the air/gas mixer. What to check first and why the gas valve should stay closed up.
RinnaiRinnai Code 14: Thermal Fuse Lockout
Rinnai code 14 means the thermal fuse or overheat circuit is open. Why it happens, why it must not be bypassed, and when a repeat needs a pro.
RinnaiRinnai Dead After a Power Outage
A Rinnai that won't heat after a power outage may have a tripped GFCI, a controller set to Off, a lockout code, or freeze damage.
RinnaiRinnai Error Code 12: Flame Failure
Rinnai code 12 means the burner lit and then lost flame. Common causes like gas supply, venting, or a dirty flame rod, and when to stop resetting.
RinnaiRinnai Goes Cold After a Few Minutes
A Rinnai that goes cold after a few minutes usually has flow dropping below minimum, flame loss (code 12), or scale overheating (code 16).
RinnaiRinnai Hot Water Heater Code 10
Rinnai code 10 means blocked air supply or exhaust. Common causes like snow, nests, or a crushed vent, and why the unit shouldn't keep firing.
RinnaiRinnai Tankless With No Hot Water
A Rinnai with no hot water usually has no 120 V, no flow signal, a lockout code, or a gas or ignition fault. Read the display first.
RinnaiRinnai Water Heater Code 25
Rinnai code 25 is a condensate problem: a full trap, a kinked or frozen hose, or a failed condensate pump. What to check and when to call a pro.
TakagiTakagi Code 111: Ignition Failure
Takagi code 111 means ignition failure after three tries. Common causes like a closed gas cock or dirty flame rod, a safe reset, and next steps.
TakagiTakagi Tankless Problems: Codes & Fixes
Takagi tankless not heating? Most lockouts are air or exhaust faults (10), ignition or flame loss (11/12), or overheating from scale (14/16).
TakagiTakagi Tankless Water Heater Not Heating
A Takagi tankless that will not heat needs flow, power, gas, ignition, or scale checks. Photograph the code.
RV
7 guidesFurrion Tankless E1 Ignition Failure
Furrion tankless E1 means ignition failure: the board never proved flame. Causes include LP supply, low 12 V, spark, or the flame probe.
FurrionFurrion Tankless Water Heater Troubleshooting
A Furrion tankless that is cold or flashing E1 needs power, flow, gas, or ignition checks. Photograph the code.
GirardGirard Tankless Reset Button: Clear a Lockout
How to clear a Girard GSWH-2 lockout with a faucet or 12 V reset, when one reset is reasonable, and which codes or smells mean stop.
GirardGirard Tankless Troubleshooting: Codes & Lockouts
Girard RV tankless not heating? Most cases are an E1/E2 ignition lockout, low 12 V, an ECO trip, a probe fault, or freeze mode. What each means.
RVRV Water Heater Fault Light On
The red light on an RV water heater switch usually means a DSI ignition lockout. What it means, one safe reset, and when to stop.
SuburbanSuburban Tankless Troubleshooting
A Suburban Nautilus tankless not heating usually has an E1/E2 ignition lockout, low flow, low 12 V, an overheat code, or freeze damage.
TrumaTruma Water Heater Flashing Light Codes
A flashing Truma AquaGo or Combi light signals a lockout or warning. How to read the blink pattern or code, and when one reset is reasonable.
Troubleshooting
22 guides5 Flashes on Water Heater: What It Means
Five flashes is a brand-specific code — usually the upper element on electric, or a gas-valve/false-pilot fault. Decode it before you reset.
American Water HeaterAmerican Water Heater Troubleshooting
American water heaters share A. O. Smith hardware. Diagnose a cold, blinking, or leaking unit by reading the LED count and finding the wet part.
A. O. SmithAO Smith Blinking Green Light Codes
A slow green blink on an A. O. Smith gas valve is often normal. Two or more flashes is a fault code. How to count the pattern and read it.
A. O. SmithAO Smith Blinking White Light
A white or pale LED blinking on an A. O. Smith gas valve can be normal, a call for heat, or a lockout. How to tell them apart from the count.
A. O. SmithAO Smith Water Heater Blinks 3 Times
Three flashes on an A. O. Smith means different faults on electric, power-vent, and atmospheric models: thermistor, pressure switch, or other.
BoschBosch Water Heater Troubleshooting
Bosch troubleshooting for Therm and Greentherm tankless, AquaStar, Powerstar electric, and Tronic mini-tanks. Codes, flow, power, and leaks.
Bradford WhiteBradford White No Status Light
A dark Bradford White status light can mean the control is off, a dead thermopile, a failed ICON, or no 120 V on power-vent models.
Bradford WhiteBradford White Water Heater Beeping
ICON gas tanks don't beep. A beeping Bradford White is usually an Infiniti tankless, AeroTherm hybrid, power-vent board, or a leak sensor.
TroubleshootingFlashing Green Light on a Water Heater
A flashing green light on a water heater is often normal. Two or more flashes usually means a brand-specific fault code. How to read it.
GE / GeoSpringGeoSpring FF Code: EXV Out of Range
GE GeoSpring F-F (FF) means the electronic expansion valve is out of range, often a sealed-system problem. What you can check before calling a pro.
RelianceReliance 6-06: No Heat, Light, or a Leak
The Reliance 6-06 is an A. O. Smith-built gas or electric tank. Diagnose no heat, the status light, or a leak by fuel type.
RelianceReliance Status Light Not Blinking
A dark Reliance status light can mean the pilot is out, a dead thermopile, the control is off or failed, or no power on electric models.
RheemRheem Water Heater No Status Light
A dark Rheem status light can mean no 240 V, a failed thermostat or ECO on electric models, or a pilot, thermopile, or control fault on gas.
RichmondRichmond Water Heater Troubleshooting
Richmond water heaters use Rheem hardware. Diagnose a cold, flashing, or leaking unit by fuel type: element, ECO, gas lockout, or leak.
RuudRuud Hot Water Heater Troubleshooting
Ruud is Rheem's wholesale brand. Diagnose a cold, flashing, or leaking Ruud by fuel type: element, ECO, gas lockout, or a leak.
U.S. CraftmasterUS Craftmaster: No Heat, Flashes, or a Leak
U.S. Craftmaster tanks share A. O. Smith/State hardware. Diagnose a cold, blinking, or leaking unit by counting the LED and finding the wet part.
TroubleshootingWater Heater Alarm Going Off? Find the Beep
A beeping water heater is usually a tankless lockout, hybrid alarm, power-vent board, or leak sensor, or a nearby smoke or CO alarm.
TroubleshootingWater Heater Beeping After a Power Outage
A water heater beeping after an outage usually has a tankless or hybrid lockout, a dry-fire alarm, a power-vent fault, or a leak sensor alert.
TroubleshootingWater Heater Beeping and No Hot Water
Beeping with no hot water usually means a tankless or hybrid lockout, a dry-fire alarm, a power-vent fault, or a leak sensor that cut the heat.
TroubleshootingWater Heater Blinking Red Light
A blinking red water heater light is usually a fault, not normal operation. How to count the flashes and read them for gas, electric, and tankless.
TroubleshootingWater Heater Status Light Blinking 3 Times
Three flashes on a water heater status light means different faults by brand: an ECO trip, a thermistor, or a pressure switch that won't close.
TroubleshootingWater Heater Status Light Blinking 6 Times
Six flashes on a water heater status light can mean a thermostat or thermistor fault on electric models, or an FVIR or valve fault on gas.