Which models this covers
A.O. Smith GCV, GCVH, GVR, GCVL, GVRL, GCVT, XCV, XVR, XCVL, XGV, XVRL, XCVT and Series 300/301 gas models with a Honeywell/Resideo WV8840-type control (A.O. Smith handbook 327726-001), plus the Resideo WT8840/WT8860 replacement controls. Codes differ between control boards, so check the code chart printed on your unit or in its manual if your model isn’t listed.
How to read the code
Count the flashes of the status light on the gas control. A single flash about every 3 seconds is normal. When two errors are present, the control can show both, higher flash count first.
Status light codes
| Code | What it means | What to do |
|---|---|---|
| 0 (off) | Control off or pilot out | Relight following the label. If it won’t stay lit, the thermal switch may have tripped: remove any flammable vapors nearby and call a pro.Pro |
| Solid | Pilot recently went out (thermopile cooling), or the control is in OFF mode | Turn the knob to OFF, wait 10 minutes, then relight. |
| 1 | Normal (“heartbeat”). Faster strobing while heating on Resideo controls | None. |
| 2 | Thermopile voltage low | Reseat the black thermopile connector and the thermal-switch connectors. If it continues, call a pro.Pro |
| 4 | ECO / temperature cut-out limit reached | Call a pro.Pro |
| 5 | Water temperature sensor failure | Call a pro.Pro |
| 6 | WT8860 only: combustion chamber high limit | Call a pro.Pro |
| 7 | Internal control / electronics failure | Call a pro.Pro |
| 8 | Power off failure: control didn’t power down with the knob at OFF | If you can see the pilot with the knob at OFF, the valve is stuck: call a pro. If not, wait 10 minutes and relight.Pro |
| 9 | WT8860 only: door sensor failure | Call a pro.Pro |
| 10 | WT8860 only: abnormal combustion temperature | Clean the air intake screens. If it returns, call a pro.Pro |
Sources
These codes are transcribed from the manufacturer’s own documentation. Many websites repeat codes that don’t match the manuals, so when in doubt, trust the chart on your unit.
- A.O. Smith Residential Gas Handbook 327726-001
- Resideo WT8840/WT8860 gas control (34-00013EF)
- A.O. Smith support: status light flashes
Code pointing to a big repair? Check whether to repair or replace before you pay for it.
Frequently asked questions
What does 2 flashes mean on an A.O. Smith water heater?
Two flashes means the thermopile voltage is low. A.O. Smith’s support guidance is to check that the black thermopile connector and the thermal-switch connectors are fully seated. A technician can measure the thermopile, which needs replacing if it reads under about 350 mV.
What does 4 flashes mean on an A.O. Smith water heater?
Four flashes means the ECO (energy cut-off) or temperature limit was reached. A.O. Smith’s handbook calls for replacing the gas control. Call a pro.
Does this apply to State water heaters?
State is owned by A.O. Smith and many State gas models use the same Honeywell/Resideo control. Confirm with your model’s manual, because we didn’t find a State-branded code chart.