An American water heater carries a badge that confuses people at the parts counter, and it should not. American Water Heater Company builds the ProLine gas and electric tanks, and it is an A.O. Smith company. A.O. Smith bought American back in 2006. So the gas control valve, the Flame Guard status-light chart, and the serial-date format on your American tank are the same ones on an A.O. Smith, State, Reliance, or Whirlpool unit. That is good news when something breaks: the codes are documented and the parts are on the shelf. The first move on any dead American is not the pilot or the breaker. It is reading the rating plate for the model, the serial, and whether you have a standard atmospheric tank or a power-vent one, because that decides which flash chart applies.
| Brand family | American / ProLine, an A.O. Smith company since 2006 |
| Shares parts with | A.O. Smith, State, Reliance, Whirlpool, U.S. Craftmaster |
| Normal gas status light | 1 flash every 3 seconds |
| Pilot out | LED dark, no flash |
| Low thermopile | 2 flashes (weak pilot / worn thermopile) |
| Over-temperature | 4 flashes |
| Thermopile floor | ~350 mV, replace below on a lit pilot |
| Recommended temperature | 120 F |
| TPR valve opens at | 210 F or 150 psi |
| Serial date code | first 2 digits year, next 2 digits week |
Key takeaways
- American is an A.O. Smith brand (acquired 2006). Its codes and parts are current and cross-reference to A.O. Smith, State, Reliance, and Whirlpool.
- Gas: one status-light flash every three seconds is normal. Read the count off the chart on your own valve; power-vent Powerflex models use a different chart.
- Two flashes is low thermopile voltage, usually a weak or dirty pilot. Four, five, and seven are stop-and-diagnose gas-valve faults.
- Electric: the red ECO reset lives on the upper thermostat. Breaker off first, reset once, and a repeat trip means a real fault.
- Set it to 120 F. The relief valve is never capped. A serial starting like 9746 means week 46 of 1997, so you can date the tank in ten seconds.
Step zero: read the rating plate and the serial
Before you touch the pilot or the breaker, find the rating plate on the side of the tank and read three things: the model number, the serial number, and whether you have a standard atmospheric gas tank or a power-vent one. The model tells the parts counter exactly what fits. The serial, in the black box labeled SER NO near the top of the label, dates the tank: the first two digits are the year and the next two are the week. A serial that starts 1512 is week 12 of 2015. The vent type matters because a standard atmospheric American reads the Flame Guard flash chart below, while a power-vent Powerflex model runs a different code set with end-switch and lockout faults. Photograph the plate. Because American is an A.O. Smith brand, every part you order cross-references to A.O. Smith, so there is no dead-brand scramble here.
No hot water: read the light, then the reset
No hot water is the call that starts most American troubleshooting, and the split is by fuel type. On a gas American, look at the status light on the gas control valve near the base of the tank. One flash every three seconds means it is fine, pilot lit and valve powered. A dark light with no flash means the pilot is out. Two flashes is low thermopile voltage, usually a weak or dirty pilot flame that does not fully wrap the sensor, a worn thermopile, or a gas valve going bad. Four flashes is over-temperature. Five is a temperature-sensor fault. Seven is a gas control electronics failure. Match your count to the chart printed on your own valve, and remember a power-vent Powerflex reads a different map with end-switch and retry-lockout codes.
On an electric American with no hot water, the usual culprit is the ECO, the red high-limit reset button on the upper thermostat. Before you go near it, kill the breaker, because the panel you are opening sits on 240 volts and the reset button is right next to live terminals. With power off, fold back the insulation, press the red button until it clicks, then button everything up before restoring power. The ECO trips only when the water really overheated, so a reset that holds is the end of it. If it trips again within a day, you have a stuck thermostat or an element shorted to the tank, not a nuisance trip, and that is where you stop resetting and diagnose. A tripped ECO cuts both elements, so it usually leaves no hot water at all. Lukewarm water instead points at a single dead element.
When the safety trips twice, stop resetting
A four-flash over-temperature code and an electric ECO that trips a second time both mean the water genuinely overheated. That is a real hazard, not a nuisance. Do not keep resetting a safety device that is doing its job. Find the overheating cause, usually a stuck thermostat or a shorted element, or call a licensed tech.
Not enough hot water, or it runs out fast
Running out is a different problem from no hot water, and the difference points at the cause. On an electric American, a burst of hot that turns lukewarm halfway through a shower is the classic sign of a dead lower heating element. The upper element heats the top of the tank for the first few gallons, then the lower element carries the rest, so when it fails you get a short run of hot followed by cold. On a gas American the same short-supply feeling usually traces to a low temperature setting, a partly clogged burner, or a thick sediment layer insulating the flame. Check the dial before you condemn a part.
Sediment is the quiet thief here. Mineral scale on the tank floor steals usable volume and burner efficiency, so a 40 gallon American starts behaving like a 30, and it drives the popping and rumble you hear as trapped water flashes to steam under the layer. A yearly drain and flush is both fix and prevention, though on a tank well past ten years the capacity loss can be permanent once the scale bakes hard onto the steel.
The pilot and thermopile problem
A two-flash code, or a pilot that lights and dies the second you release the gas knob, is almost always the thermopile. It is the sensor the pilot flame heats, and its small voltage is what holds the main gas valve open. If the pilot flame is weak, off-color, or does not fully envelop the sensor, the voltage sags and the valve closes. Clean the pilot orifice and the flame sensor, then relight per the Flame Guard legend on the burner door: knob to OFF and wait, then to PILOT, hold the knob fully in, click the red piezo igniter until the pilot lights, and keep the knob pressed about 60 to 90 seconds so the thermopile warms enough to power the valve. If the pilot holds and you get one flash every three seconds, you are done. If a tech tests the thermopile on a lit pilot and it reads below about 350 millivolts, replace it, a cheap part that cross-references to A.O. Smith.
Leaks, the relief valve, and the tank body
Where an American leaks decides whether it is a five-dollar fix or a new heater. A drip from the relief valve during a heating cycle can be normal thermal expansion. Open a hot faucet, and if the drip stops, that was expansion pressure with nowhere to go, and the cure is an expansion tank on the cold inlet. A relief valve that drips steadily otherwise is worn or has sediment on its seat, and it gets replaced, never capped. American tanks are certified for 150 psi working pressure, and that TPR valve is the tank's last safety, set to open near 210 degrees or 150 psi. Plugging it turns a water heater into a bomb. A leak at a fitting or union up top can often be resealed. The one leak nobody fixes is water weeping from the body or bottom of the tank, which means the steel corroded through, and that is a replacement.
Gas vs electric: where the American faults live
The two fuel types fail in their own ways, and knowing which side of the fence you are on cuts the diagnosis in half. The table below lines them up so you can jump to the right check.
| Symptom | Gas American | Electric American |
|---|---|---|
| No hot water | Read the status light: dark = pilot out, 2 flash = thermopile, 4/5/7 = valve fault | Reset the ECO once with breaker off; repeat trip = element or thermostat |
| Runs out fast | Low dial, sediment, or a partly clogged burner | Dead lower element (hot then cold mid-shower) |
| Too hot / scalding | Turn the dial to 120; 4-flash over-temp points at the valve | Both thermostats set high, or a stuck upper thermostat |
| Where the reset is | No user reset; the status-light code is the diagnosis | Red ECO button on the upper thermostat, behind the panel |
| Main parts | Thermopile, pilot assembly, gas control valve | Upper/lower elements, upper/lower thermostats, ECO |
Which American do you have, and what fits the situation
American sells a few tank families under the ProLine name, and the right next step depends on which one is on your wall and how old it is. Read the serial to date it, then match your case below.
Atmospheric ProLine gas
The common gas American. Uses the Flame Guard status light: 1 flash every 3 seconds is normal, 2 is thermopile, 4/5/7 are stop-and-diagnose valve faults. Pilot and thermopile are homeowner-friendly; a valve fault on an old tank leans toward replacement.
Powerflex power-vent gas
Has a blower and a different diagnostic chart with end-switch, TCO, and retry-lockout codes, not the simple 1-through-7 count. Read the label on this valve specifically and check the vent and pressure switch before condemning the control.
ProLine electric
Two elements, two thermostats, and the red ECO on the upper thermostat. No hot water starts at the ECO with the breaker off; hot-then-cold is the lower element. Elements and thermostats are cheap and cross-reference to A.O. Smith.
Aging tank, big part failed
Date it by the serial. If it is near or past the 8-to-12-year window and the failure is the gas valve or the tank body, put the repair money toward a new unit with a fresh warranty instead.
The stop-and-call-a-pro line
Plenty of American work is a careful homeowner's afternoon with the breaker off and the Flame Guard legend open: relighting a pilot, resetting an ECO once, turning the dial to 120, flushing sediment, swapping an element. Because American is an A.O. Smith brand, the parts are stocked and documented, so sourcing is not the obstacle it is on a dead house brand. The stop-and-call line is where a fault keeps coming back or the failure is the tank itself. A four-flash over-temp or an electric ECO that trips a second time both mean the water is genuinely overheating, and chasing that with repeated resets wears out a safety device while ignoring a real hazard. A seven-flash electronics fault, any gas smell, and a weeping tank body are hard stops. A gas smell means leave the house first, then call the gas utility from outside, and do not flip switches or light anything. Everything above that line is reasonable homeowner territory with the power off. Everything below it is where a licensed plumber or gas tech earns the call, because the failure mode is a burn, a flood, or a combustion problem.
Frequently asked
Who makes American water heaters, and can I still get parts?
American Water Heater Company builds the ProLine gas and electric tanks, and it is an A.O. Smith company. A.O. Smith bought American in 2006, so an American tank shares the same gas control valve, the same Flame Guard status-light chart, and the same serial-date format as A.O. Smith, State, Reliance, and Whirlpool branded tanks. Parts are current and easy to get. When you order a thermopile, gas valve, heating element, thermostat, or relief valve, use the model and serial off the rating plate, and an A.O. Smith equivalent part will cross-reference. So unlike a discontinued house brand, American parts are stocked at plumbing suppliers under the A.O. Smith family.
What do the flashes on my American gas water heater status light mean?
On a standard atmospheric American gas tank with the Flame Guard system, the light on the gas control valve blinks a code and the count is the message. One flash every three seconds is the good signal: pilot lit, valve powered, nothing to do. If the light is dark, the pilot is out. Two flashes is low thermopile voltage, usually a weak or dirty pilot, a worn thermopile, or a valve on its way out. Four flashes is over-temperature. Five is a temperature-sensor fault. Seven is a gas control electronics failure. Those last three usually mean the gas valve gets replaced. Power-vent Powerflex models use a different chart with end-switch and lockout codes, so read the label on your own valve instead of trusting a count off the internet.
Where is the reset button on an American electric water heater and can I press it?
It is the red button on the upper thermostat, the ECO or high-limit cutoff, behind the upper access panel and the insulation. One rule outranks its location: shut the breaker off first, because those terminals carry 240 volts and the reset sits right next to them. With power off, fold back the insulation, press the red button until it clicks, put everything back, then restore power. The ECO only trips when the water genuinely overheats, so a reset that holds is fine. A reset that trips again within a day means a real fault, usually a stuck thermostat or an element shorted to the tank, and that is where you stop resetting and diagnose. A tripped ECO cuts both elements, so it typically leaves no hot water at all.
What temperature should I set my American water heater to?
Set it to 120 degrees Fahrenheit for most homes. That is hot enough for showers and dishes and to keep Legionella down, and low enough that a slip at the tap does not scald on contact. Every degree past 120 shortens the time hot water needs to burn skin, which matters with kids or older adults in the house. On a gas American the dial is on the control valve. On an electric American there are two thermostats, upper and lower, and both have to be set to the same number with a small flat screwdriver, breaker off. Water that runs hotter than the dial says, or will not turn down, is a failing thermostat, and on gas it can show up as a four-flash over-temperature code.
How old is my American water heater from the serial number?
American writes the date into the serial number, so you do not need a chart. Find SER NO in the black box near the top of the rating label. The first two digits are the year and the next two are the week of that year. A serial that starts 9746 was built in the 46th week of 1997. This is the same format A.O. Smith uses across its State, Reliance, and Whirlpool tanks. Age matters because a residential tank usually lasts 8 to 12 years, so a big-part failure on a unit near or past that window is often the point where a new heater beats the repair.
Should I repair or replace my American water heater?
Match the failure to the age. Small parts are worth it on a tank with life left: a thermopile, gas valve, single element, thermostat, or a worn relief valve are all normal repairs, and American parts cross-reference to A.O. Smith so they are easy to source. The replace-it signs are the ones no part fixes. Water weeping from the body or bottom of the tank means the steel rusted through, and no patch holds. A four-flash over-temp or an electric ECO that trips a second time on a ten-year-old tank, rusty hot water that stays rusty after a full flush, and heavy baked-in sediment all point the same way. When a big part like the gas valve fails on a tank past ten years, the repair money is usually better spent toward a new unit with a fresh warranty.