Where Is the Reset Button on an AO Smith Water Heater? (Gas & Electric)

It’s late, the shower runs cold, and you’re staring at a metal tank wondering where the reset button hides. Most people assume it’s behind a big red panel. It’s not. The location depends entirely on whether your unit burns gas or uses electric elements, and getting it wrong means you’ll be staring at the wrong cover plate.

This guide walks you through the exact location for both types, the correct reset procedure, and what those blinking status lights actually mean. You’ll also learn why the button trips in the first place, so you can fix the root cause instead of resetting it every morning.

Before you start, if your inspection reveals a burnt-out element, a common fix is replacing it with a compatible 100108283 heating element that meets factory specs for many AO Smith electric models. It’s a screw-in type, so the swap takes minutes.

Quick Answer: Where Is the Reset Button Located?

For electric AO Smith heaters, the reset button sits behind the upper thermostat access panel. You’ll need a screwdriver to remove the panel and peel back the insulation. It’s a small red button near the top of the upper thermostat, often labeled ‘Reset’.

For gas AO Smith heaters, there is no separate red button. The reset function lives on the gas control valve—the round dial near the bottom of the tank. You’ll see a small ‘Reset’ button on the valve body, sometimes under a flip-up cover.

If your unit has no visible button at all, check the manual. Some older models route the high-limit switch to a separate junction box on top of the tank.

Understanding Your AO Smith Model (Gas vs. Electric)

You can’t reset what you can’t find. The physical layout of your unit dictates everything. Here’s how to tell which type you have before you touch a screwdriver.

Electric Models: Behind the Upper Access Panel

Electric units have two access panels—one upper, one lower. The reset button is only behind the upper panel. The lower panel covers the lower thermostat and heating element, which usually has no reset function.

Remove the upper panel screws. Pull out the fiberglass insulation carefully—it’s itchy. You’ll see the high-limit switch (a small rectangular device) with a red button in the center or on the side. That’s your target.

Gas Models: On the Gas Control Valve

Gas units have a large gas valve at the bottom front. It looks like a plastic dial with temperature markings. The reset button is a small, often recessed button on this valve. On newer models, it’s a tiny red or black button labeled ‘RESET’. On older ones, you might need to press a small pin with a paperclip.

If you see a separate red button on the tank body itself (not the valve), that’s a thermal cutoff switch, not the standard reset. Pressing it works the same way, but it’s a different component.

Step-by-Step Reset Instructions

Safety first: turn off the power or gas before you open anything. For electric, switch off the breaker at the panel. For gas, turn the gas valve to ‘Pilot’ or ‘Off’.

How to Reset an Electric AO Smith Water Heater

1. Turn off the dedicated circuit breaker for the water heater.
2. Remove the upper access panel with a screwdriver.
3. Fold back the insulation and the plastic safety cover (if present).
4. Locate the red reset button on the high-limit switch.
5. Press the button firmly until it clicks. It should stay depressed.
6. Replace the safety cover, insulation, and access panel.
7. Restore power at the breaker.
8. Wait 15 minutes and check for hot water at a faucet.

Pro tip: If the button pops back out immediately, the high limit is still tripped. Don’t force it. Something is overheating the tank.

How to Reset a Gas AO Smith Water Heater

1. Turn the gas control valve to ‘Off’. Wait 5 minutes for any lingering gas to dissipate.
2. Locate the reset button on the valve. It may be under a small rubber flap.
3. Press and hold the button for 10 seconds. You might hear a faint click.
4. Release the button and turn the valve back to ‘Pilot’.
5. Follow the lighting instructions on the valve label to relight the pilot.
6. Once the pilot is lit, turn the dial to your desired temperature setting.

If the pilot won’t stay lit after a reset, the thermocouple is likely weak. That’s a separate repair, not a reset issue.

Decoding the Status Light Blinks (Error Codes)

Modern AO Smith gas heaters use a blinking status light to tell you what’s wrong. The light is on the gas control valve. Count the blinks between pauses.

Blinks	Meaning	What To Do
1 blink	Ignition failure	Pilot won’t light. Check the pilot assembly and gas supply.
2 blinks	Thermocouple or flame sensor issue	Clean or replace the thermocouple.
3 blinks	Overheating / High limit trip	Reset the button. If it trips again, check for sediment buildup.
4 blinks	Blower failure (power vent models)	Check the blower motor and venting for blockages.
5+ blinks	Gas valve or control board fault	Call a professional. This isn’t a DIY fix.

Electric models rarely have error lights. If your electric unit has a blinking light on the top thermostat, it usually indicates a tripped high limit or a failed sensor. Press the reset once. If it blinks again within an hour, test the thermostat.

Why the Reset Button Keeps Tripping (Common Causes)

A reset button that trips once is an anomaly. One that trips weekly is a warning. Here’s what usually causes it.

• Sediment buildup: A thick layer of minerals at the tank bottom traps heat. The water around the upper element gets too hot, tripping the high limit. Flushing the tank annually prevents this.
• Failed thermostat: A stuck thermostat sends continuous power to the element. The water boils, steam builds, and the high limit shuts everything down.
• Bad heating element: A shorted element draws excessive current, overheating the wiring and the limit switch.
• Loose wire connection: A loose terminal on the thermostat creates resistance, which creates heat. That heat can trip the limit even if the water temp is fine.
• Incorrect thermostat setting: Setting the dial to ‘Very Hot’ (150°F+) pushes the system close to the limit’s trip threshold. Keep it at 120°F–125°F.

The most common cause I see in the field is sediment. Homeowners reset the button, get a day of hot water, then it trips again. They assume the element is bad. It’s usually just a tank full of scale.

What to Do If the Reset Button Won’t Stay Reset

If you press the button and it springs back, or if it resets but trips again within 24 hours, stop resetting it. You have a genuine fault. Here’s the diagnostic path.

Testing the Thermostat with a Multimeter

This test takes five minutes and tells you if the thermostat is the culprit. You’ll need a digital multimeter set to resistance (ohms).

1. Turn off power at the breaker.
2. Remove the upper access panel and fold back the insulation.
3. Disconnect the two wires from the upper thermostat terminals.
4. Set your multimeter to the lowest ohms setting (200 or 400).
5. Place one probe on each thermostat terminal.
6. A healthy thermostat reads near zero ohms (closed circuit).
7. If you read infinite resistance (OL), the thermostat is open and needs replacement.

Also test the high-limit switch itself. With the reset button pressed in, it should read near zero ohms. If it reads OL, the switch is blown and must be replaced.

If both test fine, the problem is likely the heating element. A shorted element will trip the breaker or the limit. Test it by checking resistance between the element’s two screw terminals. You should see a low reading (10–20 ohms). If you see zero or infinite, replace the element.

Safety Precautions: When to Call a Professional

Some situations require a licensed plumber or electrician. Don’t push past your comfort zone here.

• Gas smell: If you smell rotten eggs near the heater, leave the house and call your gas company. Do not touch any electrical switches.
• Water leaking from the tank: A leaking tank means internal corrosion. Resetting won’t help; you need a replacement.
• Breaker trips immediately: If the breaker trips the moment you restore power, you have a short. This can cause a fire. Call an electrician.
• Repeated overheating: If you’ve reset the button three times in a week, you have a systemic issue. A professional can flush the tank and test all components safely.

One honest caveat: I’ve seen homeowners replace thermostats and elements based on internet advice, only to find the real issue was a corroded wire connector hidden behind the insulation. A pro with a thermal camera finds that in minutes. Sometimes the service call is worth it.

Preventing Future Trips: Maintenance Tips

You can cut reset trips by 90% with routine maintenance. Here’s what works.

• Flush the tank twice a year: Connect a garden hose to the drain valve, open it, and let the water run until clear. This removes sediment before it insulates the tank.
• Check the pressure relief valve: Lift the lever monthly. A quick burst of water means it’s working. If it dribbles or leaks, replace it.
• Inspect the anode rod every 2 years: A depleted anode rod accelerates corrosion. Replace it before the tank starts leaking.
• Keep the thermostat at 120°F: This is hot enough for showers and below the high-limit trip point.
• Tighten electrical connections annually: Loose wires create heat. Turn off power and check the terminals on the thermostat and elements.

If you’re replacing an element, pick a quality one. The ATEEfaee replacement element is built to resist corrosion and mineral buildup, which directly addresses the most common cause of reset trips.

Frequently Asked Questions

Can I reset my AO Smith water heater without turning off the power?

You can, but you shouldn’t. The reset button is exposed metal, and the thermostat terminals carry 120V or 240V. One slip with a screwdriver and you’re getting a shock. Kill the breaker first. It takes ten seconds.

Why does my AO Smith water heater have no reset button?

Some older electric models used a manual-reset thermal cutoff that looks like a small cylinder, not a button. It’s still in the upper access panel. On gas models, the reset function is built into the gas control valve and may be recessed. Look for a small hole marked ‘RESET’ that requires a paperclip.

How often should the reset button be pressed?

Never, under normal operation. The reset button is a safety device, not a routine control. If you’re pressing it more than once a year, something is wrong. Investigate the cause before resetting again.

What’s the difference between the reset button and the circuit breaker?

The circuit breaker protects the wiring in your house from overloads. The reset button (high-limit switch) protects the water heater from overheating. A tripped breaker means an electrical fault. A tripped reset means a thermal fault. They’re independent systems, though a shorted element can trip both.

Will resetting the water heater damage it?

Pressing the button once won’t damage anything. Pressing it repeatedly while a fault exists can damage the thermostat or element, because the system keeps trying to run under fault conditions. Treat the reset as a diagnostic tool, not a fix.

Three Mistakes to Avoid

Mistake 1: Resetting without flushing. If the tank is full of sediment, you’ll reset it, get hot water for a day, and it’ll trip again. Flush first, reset second.

Mistake 2: Ignoring the blinking light. The status light is telling you exactly what failed. Count the blinks before you touch anything. That information saves you an hour of guessing.

Mistake 3: Replacing parts randomly. Buying a new thermostat when the problem is a $10 thermocouple wastes money and time. Test with a multimeter before you order anything.

What to Remember When You’re Staring at the Tank

• Electric resets live behind the upper access panel, not the lower one.
• Gas resets live on the gas control valve, not the tank body.
• Press the reset once. If it trips again, you have a fault, not a fluke.
• Count the status light blinks on gas models—they map to specific error codes.
• Flush the tank twice a year to prevent 90% of reset trips.
• Test the thermostat and element with a multimeter before buying parts.
• Call a pro if you smell gas, see leaks, or trip the breaker repeatedly.

For more context on how your heater interacts with your home’s plumbing, check out this water heater impact guide. And if you’re comparing brands before a replacement, this AO Smith vs Rheem breakdown covers the trade-offs.