No Hot Water
AO Smith Water Heater
Severity: ModerateWhat Does This Error Mean?
An AO Smith water heater with no hot water has either lost power (electric), pilot/gas (gas), or has a failed heating element or thermostat. Check the breaker or pilot first.
Affected Models
- AO Smith ProMax
- AO Smith Signature
- AO Smith Signature Premier
- AO Smith Vertex
- AO Smith Effex
Common Causes
- Tripped circuit breaker (electric)
- Pilot out or gas supply off (gas)
- Failed upper or lower heating element (electric)
- Failed upper or lower thermostat
- Tripped high-temperature cutoff (manual reset)
How to Fix It
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Check the circuit breaker (electric units).
AO Smith electric water heaters use a double-pole 240V breaker. If tripped, reset it. A breaker that trips again immediately suggests a shorted heating element or wiring fault — call a technician.
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Reset the high-temperature cutoff.
Open the upper access panel on an electric heater. Press the red Reset button on the upper thermostat. If it trips repeatedly, the thermostat or heating element is faulty.
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Check the pilot light (gas).
On standing-pilot models, look at the pilot through the inspection window. If out, follow the relight procedure printed on the heater. If it will not stay lit, see the Pilot Won't Stay Lit guide — most often a thermocouple issue.
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Test heating elements with a multimeter (electric).
Turn off the breaker first. Test each element terminal pair for continuity. No continuity means the element is broken and must be replaced.
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Verify thermostat settings.
Check that thermostats are set to a normal temperature (around 120°F). A thermostat that has been turned all the way down or has failed will produce cold water from a healthy tank.
When to Call a Professional
If basic checks do not restore hot water, a plumber or licensed technician should diagnose. Heating element replacement is DIY-feasible; gas burner repairs typically require professional service.