AO Smith Water Heater Not Heating: Common Causes and How to Fix Them
It can be frustrating when your hot water isn’t working. If your AO Smith water heater isn’t heating, you’ll want to troubleshoot the issue fast. From a tripped breaker to a faulty thermostat, we can help you diagnose and fix the issue with ease.
Why Is My AO Smith Water Heater Not Heating?
There can be a variety of issues that can cause a water heater to not heat properly. Here are a few of the categories the problem can fall under:
- Power supply issues
- Gas supply problems
- Faulty thermostat
- Failed heating elements
- Tripped reset button
- Pilot light or ignition failure
- Sediment accumulation
- Malfunctioning gas control valve
- Water heater age and wear
1. Power Supply Problems (Electric Models)
Signs of a Power Issue
- No hot water at all
- Water heater display is off
- Circuit breaker is tripped
- Reset button repeatedly trips
How to Fix It
- Check your home's electrical panel.
- Locate the breaker connected to the water heater.
- Reset any tripped breaker.
- Verify the unit receives power.
2. Tripped High-Temperature Reset Button
Symptoms
- Suddenly no hot water
- Heating elements not activating
- Reset button has popped
How to Fix It
- Turn off power to the unit.
- Remove the upper access panel.
- Press the red reset button firmly.
- Restore power and test operation.
3. Failed Heating Element
Signs of a Bad Heating Element
- Water heats slowly
- Insufficient hot water
- No hot water at all
- Breaker occasionally trips
How to Fix It
- Use a multimeter to test the heating elements for continuity
- Replace any element that fails testing
4. Faulty Thermostat
Symptoms
- Water remains cold
- Water temperature fluctuates
- Water becomes excessively hot
How to Fix It
- Check thermostat settings.
- Ensure the temperature is set between 120°F and 140°F.
- Test the thermostat with a multimeter.
- Replace the thermostat if defective.
5. Gas Supply Issues (Gas Models)
Signs of a Problem
- Burner won't ignite
- No hot water
- Gas control valve flashing error codes
How to Fix It
- Verify the gas supply valve is open.
- Check if other gas appliances are working.
- Confirm natural gas service is active.
- Inspect for gas line obstructions.
6. Pilot Light Won't Stay Lit
Symptoms
- No hot water
- Pilot flame repeatedly goes out
- Burner never ignites
Common Causes
- Dirty pilot tube
- Faulty thermocouple
- Drafts extinguishing the flame
- Gas control valve failure
How to Fix It
- Follow the manufacturer's relighting instructions found on the water heater's label.
7. Electronic Igniter Failure
Signs
- Clicking sounds without ignition
- Ignition failure error codes
- Burner won't light
How to Fix It
Inspect the following aspects:
- Igniter assembly
- Wiring connections
- Control board
- Gas valve operation
8. Sediment Buildup in the Tank
Warning Signs
- Reduced hot water supply
- Rumbling or popping noises
- Longer heating cycles
- Higher energy bills
How to Fix It
Follow these instructions to flush the tank:
- Turn off the power or gas.
- Shut off the water supply.
- Connect a hose to the drain valve.
- Drain and flush until water runs clear.
- Refill and restore power.
9. Defective Gas Control Valve
Symptoms
- Burner doesn't ignite
- Error codes on the control panel
- Inconsistent heating
- Pilot light problems
How to Fix It
- Most cases will require that the gas control valve be replaced.
10. Water Heater Has Reached the End of Its Life
Signs It's Time for Replacement
- Frequent repairs
- Tank leaks
- Corrosion
- Reduced efficiency
- Persistent heating problems
For more information on cleaning or troubleshooting, check out our AO Smith manuals and diagrams.