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Error codes · A. O. Smith · Water heaters

A. O. Smith water heater error codes: count the flashes — the light is the whole code.

A gas water heater has no display. Its gas control blinks a status light, and the number of flashes between pauses is the code — one flash every few seconds is a heater running right, four flashes is a heater that shut itself off. A power-vent heater blinks a longer pattern on the control under its blower, an electric heater with the electronic thermostat prints an E code, and the hybrid prints words on its screen. Find your heater's section below. Most of what the light says is a part on a gas line, and that part is a licensed installer's; the checks here are the ones that are yours.

Covers: 2015-and-newer A. O. Smith, State and American gas heaters with the self-powered gas control and a status light (Signature, Signature Premier, ProLine, ProMax), the power-vent heaters (Signature 500, GPVL, GPVT, GPVX), the electric heaters (Signature, Signature Premier, ProLine) and the hybrid heat pump (HPTU, HPTS).

Jump to the codes Text (573) 353-8511
Jump to a code · 29 on this page

The code as the display prints it; an older spelling sits under it on the card.

A. O. Smith · First

Before you clear it

A gas water heater's control blinks a status LED — count the flashes between pauses; an electric or a hybrid heater with a screen prints an error code.

1

Reading the light: the status light is on the gas control at the bottom front of the tank (on a power vent, on the control under the blower). The pilot must be lit for it to blink at all. Count the flashes between pauses — a power vent splits some codes with a one-second gap, so six flashes, a pause, two flashes is the six-two code.

2

The reset on a gas heater is the pilot: turn the gas control knob to OFF, wait ten full minutes (the control enforces that wait itself), then follow the lighting label on the tank. Up to 90 seconds of steady pilot pass before the light starts to blink. A power vent resets by its power — switch it off for 20 seconds and on.

3

A light that will not come on at all after three lighting tries: take the outer door off the bottom of the tank and press the small reset button on the thermal switch (the flat switch on the door's inner cover). It trips when the burner is starved for air — a lint-packed screen around the base, or a closet with the door shut.

4

Gas, venting, 240V and the water lines are a licensed installer's work — the parts below are named so the call is a short one, not so they are replaced at home. A smell of gas is never a wait-and-see: do not touch a switch, leave the room, and call the gas company from outside. A tank that is wet at the bottom, or water on the floor around it, is a leaking tank — turn the water supply off at the valve above the heater and call it in.

5

The rating plate is the label on the side of the tank: model, serial, the date it was built and the warranty years. Every warranty call starts with the model and the serial.

Section 1 of 4

Gas heaters with a status light

The Signature, ProLine and ProMax atmospheric-vent heaters. The light sits on the gas control; its flashes repeat every three seconds.

0 flashes#1

Also printed as No flash · LED not lit · Light off

Fix at home
Code

No light — pilot out

What it means

The pilot is not lit, or it is lit and the thermopile has not warmed enough yet to power the control. No light, no hot water.

Check first
  1. Turn the gas control knob to OFF, wait ten minutes, then relight the pilot by the label on the tank. Hold the knob in — the light does not blink until the thermopile has had up to 90 seconds of steady pilot.
  2. No blink after three tries: take the outer door off and press the reset button on the thermal switch; then look through the sight glass while you try again — the room lights dimmed help.
  3. No pilot flame through the glass: the igniter is not sparking (a click but no spark is the igniter wire) or the gas is not reaching the pilot — the shut-off valve on the gas line is open, and a new install has air to bleed out of the line.
  4. A pilot you can see that never brings the light on after 90 seconds is a weak pilot (the air screen at the base packed with lint), a loose connector at the control, or the thermopile.
The fix

A relit pilot and a clean air screen clear it. A pilot that lights and will not stay, or a light that never comes on with a steady pilot, is the thermopile or the igniter — gas parts, a licensed installer's job, and under warranty a warranty call.

Red light on#2

Also printed as Solid red · Light steady

Fix at home
Code

Steady light — pilot just went out

What it means

Not a fault yet. The pilot was lit a moment ago and went out; the thermopile is still warm and the control shows a steady light while it cools.

Check first
  1. Turn the gas control knob to OFF and wait the full ten minutes — the control refuses a relight sooner.
  2. Relight by the label and watch for the blink within 90 seconds.
The fix

A pilot that stays lit after the relight was a one-off — a draft, a burp in the gas line. A pilot that keeps going out is the thermopile, a starved air screen or the gas control — the installer's.

1 flash#3

Also printed as One flash every 3 seconds

Fix at home
Code

Normal operation

What it means

Not a fault. One flash every three seconds is the heater running the way it should — pilot lit, control powered, burner answering the thermostat.

Check first
  1. Nothing to check. A heater with this light and no hot water has a setting problem (the knob turned down) or a tank too small for the draw, not a fault in the control.
The fix

Nothing to fix. The knob's HOT mark is about 120°F; each mark past it adds heat and scald risk.

2 flashes#4
Check, then call
Code

Thermopile voltage low

What it means

The pilot is lit but the thermopile — the small generator the pilot flame heats, which powers the whole control — is not making enough voltage. The control will not open the main burner on it.

Check first
  1. Turn the knob to OFF. Look at the pilot through the sight glass on the next relight: a small, weak, yellow flame is a pilot starved for air — the screen around the base of the heater is packed with lint and dust. Vacuum it.
  2. The thermopile's two wires are pushed firmly onto the gas control; a connector half off prints this.
  3. Relight after the ten-minute wait and watch the light for a full minute.
The fix

A clean air screen and firm connectors clear a weak pilot. A strong blue pilot with the connectors tight that still flashes twice is the thermopile — a part on the gas line, a licensed installer's job.

Stop & call

Two flashes with a strong pilot and tight connectors is a thermopile — a warranty call on a heater under warranty, and an installer's part on any heater. Leave the knob at OFF until it is seen.

4 flashes#5
Service call
Code

Water too hot — high-temperature shutdown

What it means

The gas control's own temperature sensor saw the water in the tank far above the setting and shut the burner and the pilot off. The code shows only right after the pilot is relit, because the shutdown put the pilot out.

Check first
  1. Relight by the label after the ten-minute wait and watch the light. Four flashes again confirms it.
  2. Turn the gas control knob to OFF and the gas shut-off valve on the supply line off.
The fix

Nothing at home clears this one. The gas control valve and thermostat is the part — it is replaced whole, by a licensed installer. Do not keep relighting it; a control that has overheated the tank once can do it again.

Stop & call

Four flashes is stop and call: knob to OFF, gas supply off, and the gas control replaced. Under warranty it is a warranty call; the water in the tank may be scalding — run the hot taps carefully until it is seen.

5 flashes#6
Service call
Code

Temperature sensor failed

What it means

The thermistor that reads the tank temperature for the gas control is open or shorted. The control cannot run the burner without it.

Check first
  1. Turn the gas control knob to OFF; relight after ten minutes once and watch. Five flashes again is the sensor.
The fix

The temperature sensor is the part — on this control it is replaced with the gas control, by a licensed installer.

Stop & call

Five flashes after one relight is a service call on the gas control. Knob to OFF until it is seen; under warranty it is a warranty call.

7 flashes#7
Service call
Code

Gas control valve failed

What it means

The gas control found a fault in itself — its valve or its electronics. It shuts the burner off and stays off.

Check first
  1. Turn the gas control knob to OFF and the gas shut-off valve on the supply line off.
The fix

The gas control valve and thermostat is the part, replaced whole by a licensed installer. Nothing at home clears it.

Stop & call

Seven flashes is a service call: knob to OFF, gas supply off, and the control replaced. Under warranty it is a warranty call.

8 flashes#8
Check, then call
Code

Knob off but the pilot still burning

What it means

The gas control knob was turned to OFF and the thermopile kept making power — either it is just slow to cool, or the pilot valve is stuck open and the pilot is still burning with the control off.

Check first
  1. Make sure the knob is at OFF and wait one full minute.
  2. Take the outer door off and look through the sight glass for a pilot flame.
  3. A flame with the knob at OFF is a pilot valve stuck open: turn the gas shut-off valve on the supply line off now.
  4. No flame: wait the ten minutes for the thermopile to cool, then relight by the label. A code that does not return was the thermopile cooling slowly.
The fix

A pilot that burns with the knob at OFF is a stuck gas control — the gas supply stays off and the control is replaced by a licensed installer. A code that returns after a clean relight is the same part.

Stop & call

A pilot flame with the knob at OFF is gas supply off and call it in — never a wait-and-see. Under warranty the gas control is a warranty call.

Section 2 of 4

Power-vent heaters

The Signature 500, GPVL, GPVT and GPVX heaters with a blower on top. The light is on the gas control under the blower; a short flash every four seconds is the heater idle, and a slow bright-and-dim heartbeat is a call for heat — both normal. A fault code is a count of flashes, then a three-second pause, repeated.

Heartbeat#9

Also printed as Short flash every 4 seconds · Idle flash

Fix at home
Code

Normal — idle or heating

What it means

Not a fault. A short flash every four seconds is the heater waiting with no call for heat; a light that swells bright and dim like a heartbeat is the burner running.

Check first
  1. Nothing to check. A heater with this light and no hot water has its setting turned down, or a tank too small for the draw.
The fix

Nothing to fix — the heater is running normally.

Two flash#10

Also printed as 2 flashes (power vent)

Service call
Code

Pressure switch stuck closed

What it means

The air pressure switch that proves the blower is moving air read closed before the blower started. A switch stuck shut, or its wiring.

Check first
  1. Switch the heater's power off for 20 seconds and on; watch the light through a call for heat.
  2. The small rubber sensing tubes from the blower to the switch are pushed on at both ends and not kinked.
The fix

A code that returns is the pressure switch or the gas control — a part, a licensed installer's job. Nothing on the switch is adjusted at home.

Stop & call

Two flashes after a power reset is a service call on the pressure switch. Under warranty it is a warranty call.

Three flash#11

Also printed as 3 flashes (power vent)

Check, then call
Code

Pressure switch open — blower not proving

What it means

The blower was told to run and the pressure switch never saw the air move. The blower is not running, or the exhaust or intake pipe is blocked, or the switch is not seeing it.

Check first
  1. The blower on top runs when the heater calls for heat — you can hear it. A blower that never starts is the blower or the control.
  2. The exhaust pipe outside is clear — a bird's nest, a wasp nest, leaves, or snow against the termination blocks it. The intake on a direct-vent model the same.
  3. The small rubber sensing tubes between the blower housing and the pressure switch are pushed on at both ends, not kinked, not cracked.
  4. The vent run has not been changed — a longer run, or more elbows, than the install book allows will not prove.
  5. Switch the power off for 20 seconds and on, and watch the light through a call for heat.
The fix

A cleared termination and seated tubes clear it. A blower that runs with clear pipes and still flashes three is the pressure switch, the vent temperature limit switch or the blower itself — the installer's, and under warranty a warranty call.

Stop & call

Three flashes with the vent clear and the blower running is a service call. A vent that is blocked is cleared from outside, never by taking the pipe apart.

Four flash#12

Also printed as 4 flashes (power vent)

Check, then call
Code

ECO high-limit lockout

What it means

The tank's water went past the energy cut-off limit and the control locked out. Cycling the power does not clear this one — it needs a hand reset, and it allows only two.

Check first
  1. The reset: turn the set-point knob on the control to its lowest setting, hold it there at least ten seconds, then turn it back to the setting you want.
  2. The reset works twice. A third ECO trip locks the gas control for good.
The fix

One reset after a one-off is yours. An ECO that trips again has a control that is overheating the tank — the gas control is the part, replaced by a licensed installer. Do not keep resetting it.

Stop & call

A second ECO lockout is stop and call: set the knob to its lowest, and have the gas control replaced. The water in the tank may be scalding meanwhile.

Six-one flash#13

Also printed as 6-1 flash · Six flashes then one

Check, then call
Code

Ignition lockout — burner would not light

What it means

The control tried to light the burner three times, never saw a flame, and locked out for an hour. The gas is off or low, the igniter is not firing, or the flame sensor is not seeing the flame.

Check first
  1. The gas shut-off valve on the supply line is open; a new install or a propane tank that just ran dry has air in the line.
  2. A propane heater: the tank is not empty.
  3. The power to the heater is steady — not an extension cord, not a tripped GFCI.
  4. Switch the power off for 20 seconds and on to clear the hour, and listen through a call for heat: the blower, then a click or a glow, then the burner.
The fix

Gas restored and a reset clear it. A heater with gas at the valve that still locks out is the hot-surface igniter, the flame sensor or the gas control — gas parts, a licensed installer's job.

Stop & call

An ignition lockout with the gas on and the power steady is a service call. A smell of gas at the heater after a lockout is leave the room and call the gas company.

Seven flash#14

Also printed as 7 flashes (power vent) · FVS lockout

Check, then call
Code

Flammable vapor sensor lockout

What it means

The sensor at the base of the heater smelled flammable vapor — gasoline, paint thinner, a propane cylinder, a spill — and the control locked the heater out. It will not run again until the sensor is reset by hand.

Check first
  1. Do not touch a switch and do not relight anything. Smell around the heater for gas; a gas smell is leave the room and call the gas company from outside.
  2. Look for what the sensor smelled — gasoline cans, paint, thinner, a mower, a propane cylinder, cleaners — and move it out of the room. Open the room and let it air for an hour.
  3. Reset the sensor by the sequence printed on the heater's label (the control's own FVS reset — the book spells it out) once the room is clear.
The fix

A clear room and the reset clear a true lockout. A lockout that returns with nothing flammable in the room is the sensor itself — a part the installer replaces, and the book says to replace it after any lockout.

Stop & call

A lockout you cannot trace to a spill or a can, or one that returns in a clean room, is a service call on the flammable vapor sensor. Never bypass it.

Eight-four flash#15

Also printed as 8-4 flash · Eight flashes then four

Service call
Code

Gas valve fault

What it means

The control found a fault in its own gas valve. It shuts the burner off and stays off.

Check first
  1. Switch the power off for 20 seconds and on. A code that returns is the valve.
The fix

The gas control is the part, replaced whole by a licensed installer. Nothing at home clears it.

Stop & call

Eight-four after a power reset is a service call on the gas control. Under warranty it is a warranty call.

Section 3 of 4

Electric heaters

A plain electric heater has no light and no code — its one control is the red reset button on the upper thermostat. The Signature Premier electric with the electronic thermostat prints E codes on its module. Every electric heater runs on 240V: switch its double breaker off before an access panel comes off, and leave the wiring to an electrician.

ECO#16

Also printed as Reset button · High limit

Check, then call
Code

High-limit reset button tripped

What it means

Not a code — the energy cut-off on the upper thermostat tripped because the water in the tank got too hot, and it cut both elements. No hot water at all, with the breaker on, is this nine times in ten.

Check first
  1. Switch the heater's double breaker off.
  2. Take the upper access panel off the side of the tank (two screws), fold the insulation back, and press the red button on the thermostat until it clicks.
  3. Panel back on, breaker on, and give the tank an hour. Hot water that returns and stays was a one-off trip.
The fix

A button that trips again inside a week has a thermostat stuck on or a grounded element — parts an electrician or a licensed installer replaces. Do not keep pressing it; the trip is the safety.

Stop & call

A reset button that trips a second time is a service call. Switch the breaker off until it is seen; under warranty it is a warranty call.

E01#17

Also printed as 1 flash (red)

Fix at home
Code

Dry fire — tank not full

What it means

The power came on with the tank not full of water, and the control stopped before the upper element burned out dry. Almost always a new install powered up too soon.

Check first
  1. Switch the breaker off.
  2. Open a hot tap at the nearest sink and leave it running until water flows in a full, steady stream — three minutes with no air spitting.
  3. Switch the breaker back on.
The fix

A full tank clears it. A heater that printed E01 after running dry for a while may have lost its upper element — no hot water after the fill is that element, an installer's part.

E02#18

Also printed as 2 flashes (red)

Check, then call
Code

Water too hot — high limit

What it means

The water went past the high limit and the control cut the elements. A thermostat stuck on, or a one-off.

Check first
  1. Switch the breaker off.
  2. Press the reset button on the thermostat (behind the upper access panel), then switch the breaker on.
  3. Hot water that returns and stays was a one-off; watch it for a week.
The fix

An E02 that returns is a thermostat or an element that will not switch off — the installer's, and never something to keep resetting.

Stop & call

A second E02 is a service call. Switch the breaker off until it is seen; the water in the tank may be scalding.

E03#19

Also printed as 3 flashes (red)

Service call
Code

Upper temperature sensor

What it means

The upper thermistor — part of the electronic thermostat — is open or shorted. The control cannot run the upper element without it.

Check first
  1. Switch the breaker off for one minute and on. A code that returns is the sensor.
The fix

The electronic thermostat is the part, replaced by an installer or an electrician with the breaker off.

Stop & call

E03 after a reset is a service call on the electronic thermostat. Under warranty it is a warranty call.

E04#20

Also printed as 4 flashes (red)

Service call
Code

Upper element circuit

What it means

The control drove the upper element and saw no current — the element is open, its wiring is off, or the thermostat's relay failed. The lower element still works, so there is some hot water, slowly.

Check first
  1. Switch the breaker off for one minute and on. A code that returns is the element or its wiring.
The fix

The upper element (and, if it tests good, the electronic thermostat) is the part — replaced with the breaker off and the tank drained below the element, an installer's or an electrician's job.

Stop & call

E04 after a reset is a service call. The lower element carries on meanwhile; under warranty it is a warranty call.

E05#21

Also printed as 5 flashes (red)

Service call
Code

Lower element circuit

What it means

The control drove the lower element and saw no current. The upper element still works, so the first few gallons are hot and the rest run cool.

Check first
  1. Switch the breaker off for one minute and on. A code that returns is the element or its wiring.
The fix

The lower element (or the thermostat, if the element tests good) is the part — replaced with the breaker off and the tank drained, an installer's or an electrician's job.

Stop & call

E05 after a reset is a service call. Under warranty it is a warranty call; the upper element carries on meanwhile.

E07#22

Also printed as 7 flashes (red)

Service call
Code

Lower temperature sensor

What it means

The lower thermistor is open or shorted. The control cannot run the lower element without it.

Check first
  1. Switch the breaker off for one minute and on. A code that returns is the sensor or its connection at the thermostat.
The fix

The lower thermistor is the part, replaced by an installer or an electrician with the breaker off.

Stop & call

E07 after a reset is a service call. Under warranty it is a warranty call.

Section 4 of 4

Hybrid heat pump heaters

The HPTU and HPTS hybrids print words on the screen on top. Three of them are the heater telling you what it is doing, not a fault. Press any button to quiet the alarm that comes with a code.

ICE#23
Fix at home
Code

Heat pump defrosting

What it means

Not a fault. The heat pump's coil frosted in a cold room and the heater is melting it off; the elements carry the load meanwhile.

Check first
  1. Nothing to check. It clears by itself in a few minutes.
The fix

Nothing to fix. A heater that shows ICE constantly is in a room too cold for the heat pump — the elements run and the savings stop; the room, not the heater, is the cause.

HPO#24
Fix at home
Code

Heat pump stepped aside

What it means

Not a fault. The room is outside the heat pump's working range (very hot or very cold), or the tank is so cold the elements are faster; the heater runs on its elements until conditions change.

Check first
  1. The room is between about 45°F and 120°F; a garage in a cold snap or a closed attic in August is outside the range.
The fix

Nothing to fix. The heat pump comes back when the room does.

SF#25
Fix at home
Code

Air filter dirty

What it means

Not a fault. The air filter on the heat pump's intake is loaded with dust and the control wants it cleaned.

Check first
  1. Slide the filter out of the top of the heater, rinse it under the tap, let it dry, and slide it back.
The fix

The code clears with the filter back in. Clean it every few months; a dirty filter makes the heat pump work harder and trips ECF below.

Edr#26
Fix at home
Code

Not enough water in the tank

What it means

The tank is not full. On a new install the power came on before the fill finished; on a running heater the supply was shut off.

Check first
  1. Open every hot tap in the house and leave them running until each flows in a full, steady stream — three minutes with no air spitting.
  2. The cold supply valve above the heater is open.
The fix

A full tank clears it. The elements never run dry on this heater — the code is the control refusing to let them.

EoF#27
Check, then call
Code

Condensate not draining

What it means

The heat pump pulls water out of the air, and that water is not getting away — the drain line is blocked, the pan is full, or the condensate pump has stopped.

Check first
  1. The condensate pump (if one is fitted) is plugged in and its outlet has power — a tripped GFCI is the usual cause.
  2. The clear drain tube from the heater is not kinked, blocked or frozen; a cup of water poured into the pan should run away.
  3. The pan under the heat pump is not overflowing, and the heater is level.
  4. The small control wires to the condensate pump are connected.
The fix

A cleared line or a restored outlet clears it. A pump with power that will not run is the condensate pump — a part the installer replaces.

Stop & call

EoF with the drain clear and the pump powered is a service call on the condensate pump. The heater runs on its elements meanwhile.

EPL#28
Check, then call
Code

Supply voltage too low

What it means

The power coming in is below what the control will run the compressor on. A loose connection, a brownout, or a weak circuit.

Check first
  1. Switch the breaker off for one minute and on.
  2. Both halves of the double breaker are on; a breaker that looks on but sits a hair off center has tripped on one leg — push it fully off, then on.
  3. Was there a storm or a utility brownout? The code clears once the power is steady.
The fix

A sound supply and a reset clear it. An EPL that returns on a good circuit is a loose connection at the heater's wiring or the control — an electrician's or the installer's.

Stop & call

EPL that returns on a sound 240V circuit is a service call; the wiring at the heater is an electrician's.

ECC#29
Service call
Code

Compressor not running

What it means

The control drove the heat pump's compressor and it did not run. The heater keeps making hot water on its elements; the savings stop.

Check first
  1. Switch the breaker off for one minute and on, and listen at the top of the heater for the compressor to start within a few minutes of a call for heat.
  2. The air filter is clean (SF above) and the heater has the clear space around it the install book asks for.
The fix

An ECC that returns is the compressor, its capacitor or its control — sealed-system parts, a licensed technician's job. The elements carry the house meanwhile.

Stop & call

ECC after a reset is a service call on the heat pump. The heater still makes hot water on its elements; under warranty it is a warranty call.

Warranty · When to file

When it's a warranty call

Every unit leaves with the manufacturer's full factory warranty. The codes below name a part inside the machine — once the checks have ruled out the install, the power and the hoses, call A. O. Smith's line with the model and serial, and text us if you want a hand with the claim.

Warranty help for A. O. Smith

All units are surplus inventory (open box, cancelled order, customer return, overstock, or minor scratch & dent). Every unit includes the manufacturer's full factory warranty. Please inspect thoroughly in person before purchasing — cosmetic imperfections or missing accessories are possible.

Still stuck?

Text us the model number and what it's doing — we'll point you at the next step.

A fix, a part, or a warranty call — the plate's model and serial plus one line about the symptom is all it takes to tell which.

File a warranty inquiry Text (573) 353-8511Browse InventoryOr reach us another way

These pages are educational. Every appliance is a little different — follow the manufacturer's manual and local code, and leave gas, water heater and 240V work to a licensed installer.

Read next: Water heater troubleshooting (no code) · Water heater care & upkeep · Water heater codes on other brands

All error codes