State Tankless E65 Error — What It Means
E65 does not appear in any verified State or A.O. Smith tankless water heater fault code documentation. State tankless units use error codes like E1, E2, E3, E4, E5, E6, E7, E9, E10, E11, E12, E29, E31, E61, E71, E99, and E110, but E65 is not among them. If your display shows E65, first verify the exact model number and control platform on the rating plate. The code may belong to a different brand, a tank-style unit, or a misread display.
Once you confirm the correct code from your model’s manual, the most common underlying problems on State tankless units are ignition failure, flame loss, blocked air intake or venting, low gas supply, low water flow, and scale or mineral buildup on the heat exchanger or sensors. Treat this as a model verification step before attempting repairs.
Common Causes
- Incorrect model or brand family E65 is not documented for State tankless units, so the display may belong to a different manufacturer or product line.
- Gas supply restriction Closed shutoff valve, low propane tank level, or undersized gas line can prevent ignition and trigger fault codes on tankless units.
- Blocked air intake or vent Debris on the intake screen, restricted vent pipe, or incorrect vent length stops combustion airflow and causes shutdown.
- Scale or mineral buildup Hard water deposits on the heat exchanger, flow sensor, or temperature sensor reduce flow and cause sensor errors.
- Loose wiring or sensor connection Vibration, movement, or previous service work can disconnect or damage sensor wiring and control board harnesses.
Step-by-Step Fix
- Verify the model and code by reading the rating plate inside the unit and comparing the displayed code to the fault list in your model’s manual.
- Check gas supply by confirming the gas shutoff valve is fully open, testing other gas appliances in the home, and checking propane tank level if applicable.
- Inspect air intake and venting for blockage, remove any debris from intake screens, and confirm vent pipe length and elbow count match installation specifications.
- Flush and descale the heat exchanger using a tankless flushing kit and descaling solution if the unit is installed in a hard-water area or has not been serviced recently.
- Inspect all wiring and sensor connectors for looseness, corrosion, or damage, especially at the flow sensor, temperature sensor, and control board.
- Perform a soft reset by turning off power to the unit, waiting ten seconds, then restoring power and opening a hot water tap to test operation.
- Contact the manufacturer or a licensed technician if the fault persists or if the model confirmation reveals a code not covered in your documentation.
Parts Often Needed
| Part | Notes |
|---|---|
| Air intake screen | Amazon | Replace if clogged or damaged. Match the screen to your model’s combustion air inlet. |
| Flow sensor | Amazon | Required when flow detection fails or scale blocks the sensor. Order by exact model number. |
| Temperature sensor | Amazon | Used when sensor readings are erratic or out of range. Verify connector integrity before replacing. |
| Control board (PCB) | Amazon | Only replace after confirming all sensors, gas, and venting are correct. Must match your control platform. |
When to Call a Pro
Call a licensed technician immediately if you cannot locate E65 in your unit’s manual, if you are unfamiliar with gas appliance service, or if the fault returns after you have verified gas supply, venting, and performed a flush. Tankless water heaters require precise gas pressure, combustion air balance, and sensor calibration. A technician will verify the correct fault code for your model, test gas valve operation, measure inlet and outlet temperatures, inspect the flame rod and igniter, and replace any confirmed failed component with the manufacturer-approved part.