Why Does My AO Smith Water Heater Pilot Light Keep Going Out?

By SmartHomeBit Staff •  Updated: 06/06/23 •  21 min read


Do you own an AO Smith water heater? You may be dealing with the annoying issue of your pilot light going off. There are several possible causes.

The thermocouple might be faulty or damaged. Or, a blocked pilot tube due to dirt, webs, etc. could be the cause. A faulty gas control valve may be the cause.

It’s best to call a professional. They will have the right tools, knowledge, and experience to repair it properly. If you’ve attempted to troubleshoot and the problem remains, you can take these steps:

  1. Clean the burner and pilot assembly.
  2. Ensure proper ventilation.
  3. Keep combustible materials away from the heater.

Understanding the AO Smith gas water heater

AO Smith gas water heaters are a great pick for those looking for dependable and efficient hot water solutions. These heaters have a pilot light which lights the burner, making the water in the tank get to the desired temperature. But, users must be aware the pilot light may go out due to multiple reasons, such as dust, dirt, or debris in the burner assembly. Therefore, regular maintenance is a must to avoid reduced efficiency, malfunction, and even potential risks of gas leaks and fires.

It’s critical to understand the fundamentals of AO Smith gas water heaters to guarantee optimal performance and longevity. There are many components in the heater, such as a thermostat, gas control valve, and burner assembly. Each part is important in heating up the water. The thermostat regulates water temperature, while the gas control valve manages the gas supply to the burner, heating the water in the tank.

Regular maintenance is essential for the ideal operation of the AO Smith gas water heater. This includes flushing out the tank to remove sediment buildup, examining the thermostat settings, and making sure the burner assembly is clean and working properly. Not doing regular maintenance can cause reduced efficiency, malfunction, and even potential risks of gas leaks and fires.

All in all, understanding the AO Smith gas water heater is key for users to make sure they get the best performance and longevity from their heaters. Users should be familiar with the different components and their roles, potential issues that may arise, and the importance of regular maintenance. With proper care and attention, AO Smith gas water heaters can provide steady hot water for a long time.

Possible causes of pilot light going out

If your AO Smith Water Heater pilot light keeps going out, there are several possible reasons why this may be happening. In this section, we’ll take a closer look at those reasons, including:

  1. a tripped or broken thermal switch,
  2. a bad thermocouple or thermopile,
  3. a dirty air filter or flame arrestor.

We’ll also explore other possible causes, such as:

With this information, you can troubleshoot the issue and get your water heater up and running again.

Tripped/broken thermal switch

The thermal switch in an AO Smith gas water heater is a crucial safety feature. If it trips or breaks, it causes the pilot light to go out.

It’s important to act quickly if you suspect this has happened. You’ll need specialized knowledge and tools. So, contact a licensed plumber.

They’ll turn off the power and access the control panel. Then, they’ll reset the switch – either by pressing a button or flipping a switch.

If resetting doesn’t work, they’ll replace it. This is for your safety. Don’t hesitate to call a plumber if you think there’s an issue with the thermal switch. Protect your home and family – do it now!

Bad thermocouple/thermopile

Do you own an AO Smith gas water heater? Be aware of issues related to a bad thermocouple/thermopile. It can cause the pilot light to go out and interruptions in the power supply. Ignoring these can lead to energy wastage and costly repairs.

To check if your AO Smith water heater has a problem, get tools like a multimeter and manometer. Get help from experienced professionals.

If you notice any issues, get help from a professional plumber. Also, clean its air filter and flame arrestor regularly for smooth functioning.

Dirty air filter/flame arrestor

A common problem with AO Smith gas water heaters is dirty air filters and flame arrestors. This restricts airflow and stops enough oxygen reaching the combustion chamber. Result? No pilot light, no hot water.

So, we must clean or replace the air filter and flame arrestor every year during regular maintenance. Not doing so can cause serious damage.

A homeowner didn’t, and got stuck with major debris on their air filter and flame arrestor. This caused intermittent hot water availability, needing a professional to fit new components.

Clean up your AO Smith gas water heater’s air filter and flame arrestor! Avoid hassle and costly repairs.

Low oxygen

Insufficient oxygen supply to an AO Smith gas water heater could cause the pilot light to go out. This leads to a lack of hot water or none at all! It’s vital to tackle this issue ASAP to prevent any problems.

Low oxygen levels around the heater have several consequences. Uncomplete combustion can build up carbon monoxide and become a safety hazard. It can also lead to soot clogging the flame arrestor and air filter, causing overheating and insufficient heating of water.

The pilot light may go out due to other causes. These include a faulty gas valve, low gas pressure, dirty air filter/flame arrestor, backdraft in flue hood, or bad thermocouple/thermopile. You can use tools like a multimeter and manometer for diagnosis. Cleaning the air filter and flame arrestor regularly is key for optimal performance.

To sum up, paying attention to oxygen supply and performing regular maintenance are necessary for an AO Smith gas water heater. This will prevent potential safety hazards.

Backdraft in flue hood

If your AO Smith gas water heater’s pilot light won’t stay on, it could be backdraft in the flue hood. This happens when combustion gases can’t escape the venting system. There are several causes: blockages, undersized vents, bad installation, strong winds, and air pressure.

Backdraft can be dangerous – carbon monoxide poisoning and explosions. To fix it, check ventilation size with a pro, clear blockages yearly, make sure check valves and draft control systems are working right, and follow AO Smith product specs. This’ll help performance and lifespan.

Low gas pressure

Low gas pressure can be due to blockages in the fuel line. Or, a faulty regulator on the appliance. To find out, use a manometer.

Routine maintenance is a must for AO Smith water heaters. Check and clean air filters and flame arrestors. Blockages in air pathways will limit combustion airflow and fuel efficiency. Don’t assume every issue is from the gas valve. Sometimes, a pilot light is just in need of a break.

Faulty gas valve

A faulty gas valve can cause a pilot light outage on an AO Smith gas water heater. It regulates the amount of gas that goes into the burner, so if it’s malfunctioning, it won’t provide enough gas to keep the light on. This can cause flameouts or problems with heating.

Low hot water pressure or no hot water? If so, turn off your heater and contact a plumber.

To assess a gas valve, use a multimeter to check the electrical connections for continuity. With a manometer, you can measure the gas pressure coming into the unit. If these tests fail, it’s likely there’s a problem with the valve. It’ll need to replace.

In conclusion, a malfunctioning gas valve can cause issues with an AO Smith gas water heater. To diagnose it, use a multimeter and manometer before calling a plumber. Have these tools ready to investigate like a pro!

Tools needed for diagnosis

When it comes to diagnosing why your AO Smith water heater’s pilot light keeps going out, having the right tools is crucial. In this section, we’ll discuss the two essential tools you’ll need to diagnose the issue: a multimeter and a manometer. These tools can provide accurate readings on electrical and gas-related components, helping you to pinpoint the root cause of the problem with your water heater.


A multimeter is a must-have tool for diagnosing AO Smith gas water heater issues. It takes precise readings of voltage, resistance, and current. It can even measure temperatures to detect thermal switch faults. With this tool, plumbers can easily locate the faulty component.

Moreover, a manometer is used with the multimeter for more accurate testing. This helps measure pressure, making it easier to identify problems in the gas control valve or low gas pressure.

Pro Tip: Test each suspected part with the multimeter thoroughly before replacing. This will save time and money when repairing AO Smith water heaters.

Don’t know what a manometer is? It’s not a tool for measuring men!


A manometer is a great tool for diagnosing potential problems with an AO Smith gas water heater. It’s used to measure pressure, especially gas pressure. With the manometer, you can tell if there’s enough pressure for the burner to work well.

Refer to the table below to see how the manometer should be used to figure out why the pilot light went off. The first column has cause categories and the second has the corresponding manometer readings.

Cause Manometer Reading
Low Gas Pressure 3.5 inches wc
Faulty Gas Valve 11.0 inches wc in/out
Backdraft in flue hood 8.0-9.0 inches wc
Low Oxygen Use oxygen analyzer

Remember that the manometer can’t measure all the things that could be causing the pilot light issue. So, other tools like a multimeter may be needed for a complete diagnosis.

It’s best to get professional help if you’re not sure or don’t feel comfortable troubleshooting and fixing your water heater system. If you think your AO Smith water heater needs professional attention, do it right away.

In conclusion, when deciding between a mechanical manometer and an electronic one, the most important thing is to have the right tools and knowledge to diagnose and repair any water heater problems.

Differentiating mechanical and electronic water heaters

Comparing mechanical and electronic water heaters can help people pick the right one for them. The main difference between the two is their function. Mechanical water heaters use a valve, pilot flame, and thermostat to control water temperature. Electronic water heaters have a computerized thermostat and no pilot flame. They’re more efficient and consume less fuel. See the table below for a quick comparison:

Mechanical Water Heaters Electronic Water Heaters
Functionality: Valve, Pilot Flame, Thermostat Computerized Thermostat
Efficiency: Less efficient More efficient
Fuel usage: Uses more fuel Uses less fuel
Maintenance: Needs frequent maintenance Requires less maintenance

Price is another point of difference. Electronic water heaters are more costly to buy, install, and repair. But they’re more efficient and require less maintenance, which could make them cost-effective in the long run.

Individuals must take into account family size, water usage patterns, and budget when selecting between the two. For instance, large families may opt for bigger water heaters or the efficiency of electronic ones.

If someone chooses a mechanical water heater, they can keep the pilot light on by checking gas supply, cleaning the pilot orifice, and confirming the thermocouple works properly. If someone prefers an electronic water heater, they can save energy with a model with a high energy efficiency rating.

In the end, it’s important to differentiate between mechanical and electronic water heaters to find the right one. Consider cost, efficiency, maintenance needs, and family size. This will help users make an informed decision.

Preventive maintenance of the water heater

Preventive maintenance of your Ao Smith water heater is crucial to ensure it functions efficiently, and an uncleaned unit can lead to the pilot light frequently going out. In this section, we will discuss two essential elements of preventive maintenance: cleaning the air filter and flame arrestor.

Cleaning air filter and flame arrestor

The air filter and flame arrestor must be kept in good condition for efficient and safe operation of an AO Smith gas water heater. Dirt, dust, and debris can accumulate on these components, blocking airflow to the burner and pilot light. To clean them, follow these five steps:

  1. Close off the gas supply.
  2. Take off the cover panel and access the air filter and flame arrestor housing.
  3. Clean the air filter with soapy water or vacuum it. Remove debris between pleats or any other dirt that could block airflow.
  4. Use a soft brush attachment on the vacuum cleaner to clean out dirt build-up on both sides of the flame arrestor plates.
  5. Put the cover panel back in place.

Do not use a high-pressure water jet or compressed air to clean these parts. This can damage wires or sensors or move dirt into places with low-clearance gap settings. Cleaning the air filter and flame arrestor correctly will save energy, and help prolong the equipment’s life without expensive maintenance services.

Solutions for other common water heater problems

Are you experiencing slow or inadequate hot water, unusual noises, or inconsistent water temperature in your home? In this section, we’ll discuss some solutions for other common water heater problems that you may encounter. From resolving slow hot water issues to figuring out how to address unusual noises, we’ll explore some practical tips that can get your hot water system back on track.

Slow hot water

Your AO Smith gas water heater might be giving you slow hot water. This could be due to sediment and minerals at the bottom of the tank. Flushing it regularly can help. The thermostat that regulates water temperature might also be malfunctioning. Water temperatures could be inconsistent.

External factors can affect your water heater’s performance. Outdated plumbing or low water pressure in your home can be a problem. Get professional plumbing help. Waiting too long could lead to more expensive repairs later.

Not enough hot water

The AO Smith gas water heater is a must-have in any home. But, it can sometimes not provide enough hot water, resulting in discomfort. This could be due to a faulty/old heating element, sediment buildup in the tank, or a dirty air filter/flame arrestor.

The heating element is essential to heat the water. Malfunctioning/old elements can cause insufficient hot water supply. If sediment accumulates in the tank, it can lead to cold/lukewarm water. To prevent this, flushing the tank regularly is the best solution.

A dirty air filter/flame arrestor can also reduce hot water supply. It restricts air movement in the combustion chamber, reducing the heat the burner flame produces. An undersized unit may also be the problem; bigger units should be installed, with size based on physical space and estimated usage rate.

A malfunctioning thermostat can also be the cause. If it’s set too low, it can result in inefficient heating. Setting it too high increases the risk of scalding burns. Adjusting/replacing the thermostat should fix this issue.

Regular inspection and maintenance will help the unit last longer. In short, finding the root cause is important. Proper maintenance and expert assistance should be used to resolve it.

Too hot water

When it comes to hot water from an AO Smith gas water heater, too much heat can be a real problem. It can make for an uncomfortable shower and even lead to scalding. Thankfully, the temperature on the gas valve can be adjusted. But, sometimes that won’t work. In these cases, there may be an underlying issue causing the hot water to be too hot.

A common cause is a malfunctioning gas valve or thermostat. If either is faulty, they might not regulate the temperature correctly, which causes overheating. Regular inspections and preventive maintenance can help fix this problem.

Sediment buildup in the tank can also be to blame. Minerals in the water can settle at the bottom of the tank, forming sediment. This can clog the drain valve or hurt heating efficiency. To prevent overheating, a professional plumber can flush out the sediment.

It’s also important to check that all valves, filters, and other components are working properly. Defects or obstructions can cause dangerous temperature fluctuations. Therefore, it’s best to have a trained technician regularly inspect them.

Don’t blame your AO Smith gas water heater for cold showers. With care and maintenance, you can enjoy hot, but not too hot, water whenever you need it.

Hot water not available

Homeowners may find themselves without hot water from their AO Smith water heater. This can disrupt daily routines and be inconvenient. It may be caused by a malfunctioning pilot light, which stops the gas burner from heating the water. Minerals and sediments can also build up in the tank, reducing the flow of hot water.

Therefore, professional assistance should be sought to diagnose and treat the problem. This could involve replacing a broken thermocouple or thermostat, or cleaning out mineral buildup. Routine maintenance, once or twice a year, should be done by a plumbing professional. This will help catch any warning signs early, preventing costly repairs.

If issues with the water heater are not addressed quickly, it can cause further damage, leaving you without hot water for weeks. So it’s important to act immediately and get professional help, to avoid cold water troubles.

Hot water turning cold

When your water heater is not producing hot water and it’s turning cold, this is often a sign of a problem. One possible cause could be a faulty thermostat or temp control. This can lead to sudden temp changes, resulting in cold water.

Mineral buildup in the tank can also be an issue. Over time, sediment and minerals can block up the tank, reducing the amount of hot water available. Regular maintenance and flushing the tank can remove any buildups.

Leaks can also cause the hot water to turn cold quickly. Air may get into the tank and lessen the pressure.

To fix these issues, adjust the thermostat, flush out minerals or check for leaks. Professional help may be needed to replace a damaged heating element or fix a faulty valve.

Addressing these problems quickly will stop stress and hassle and ensure you have uninterrupted access to clean hot water. If your water heater is making walrus noises, call the professionals.

Unusual noises

Weird noises coming from your water heater? That’s cause for alarm! These sounds may mean trouble with the gas line – perhaps it’s loose or blocked. Don’t take this lightly – you must immediately turn off the gas supply and call a plumber.

Neglecting these sounds can cause serious damage to the heater and the area around it. So, do regular preventive maintenance. Flush out sediment from the tank, and check for leaks or weak connections. Staying alert and tending to issues right away will keep your water heater running smoothly and efficiently.

When to seek professional plumbing assistance

Dealing with an AO Smith water heater pilot light that keeps going out is tricky. If you’ve tried troubleshooting and DIY repair methods with no luck, it’s time to call a licensed plumber. They can provide an accurate diagnosis and effective solutions that meet local building codes. Plus, they’ll carry out repairs safely, protecting your property and wellbeing.

If you notice other issues like leaks or strange noises, don’t wait. Contact a plumber right away to avoid costly water damages and increase the lifespan of your appliance.

Safety should always be your priority when it comes to potentially dangerous equipment. So, if you have any problems with your AO Smith water heater pilot light or anything else, get help from a licensed plumber as soon as possible.


Pilot lights in A.O. Smith water heaters that often go out can lead to subpar performance. Causes may vary from a defective gas valve to drafts. Homeowners must do a thorough inspection to find the root cause and fix it. If the light still doesn’t stay on, component replacement may be necessary. Performing maintenance and inspections can stop malfunctions and lengthen the water heater’s life.

FAQs about Ao Smith Water Heater Pilot Light Keeps Going Out

Why does my AO Smith water heater pilot light keep going out?

There are several possible causes for why your AO Smith pilot light keeps going out, including a tripped/broken thermal switch, a bad thermocouple/thermopile, a dirty air filter/flame arrestor, low oxygen, backdraft in the flue hood, low gas pressure, or a faulty gas valve.

What tools do I need to diagnose the issue?

You may need a multimeter and manometer to diagnose the issue with your AO Smith water heater pilot light. It is also recommended to consult the user manual, as causes can vary depending on whether the water heater is mechanical or electronic.

How can a dirty air filter cause the pilot light to go out?

A dirty air filter and clogged flame arrestor can prevent sufficient airflow to the combustion chamber, causing the burner to shut prematurely or the pilot light to go out. To prevent this issue, it is recommended to clean the air filter and flame arrestor regularly as part of preventive maintenance.

What should I do if my air filter and flame arrestor are clean?

If your air filter and flame arrestor are clean, it is possible that the issue is caused by a faulty thermocouple or thermopile. Professional assistance may be needed to replace faulty parts or fix low gas pressure or faulty gas valve issues.

What are some common problems with AO Smith gas water heaters?

Common problems with AO Smith gas water heaters include slow hot water, not enough hot water, too hot water, hot water not available, hot water turning cold, pilot light issues, and unusual noises.

Do I need a professional plumber to fix my AO Smith water heater?

Depending on the issue, you may need a professional plumber to fix your AO Smith water heater. Some solutions, such as adjusting the thermostat or checking for leaks, can be done by the homeowner. However, more complex issues like replacing a thermocouple or gas control valve may require professional assistance.

SmartHomeBit Staff