E1 🟡 Repair Required
A.O. Smith Error Code E1: Thermistor Failure
⚠️ Your A.O. Smith water heater has detected a problem with one of its temperature sensors and has shut down to prevent potential overheating or other issues. You will not have hot water until this is resolved.
How to Fix A.O. Smith Code E1
- Step 1: Check the water heater's display for any other error codes. Note them down, as they may provide additional clues.
- Step 2: Reset the water heater by turning off the power at the breaker for 30 seconds, then turning it back on. This may clear a temporary error.
- Step 3: If the E1 error persists after resetting, contact a qualified HVAC technician to diagnose and repair the issue.
What Does A.O. Smith Error Code E1 Mean?
The E1 error code on your A.O. Smith tankless water heater indicates a problem with one of its thermistors. Thermistors are temperature-sensitive resistors that send temperature readings to the unit's control board. The control board uses these readings to regulate the burner and ensure safe and efficient operation. An E1 error specifically points to a failure or out-of-range reading from either the inlet or outlet thermistor. This could be due to a faulty sensor, wiring issues, or a problem with the control board itself. Because the unit cannot accurately monitor water temperature, it shuts down to prevent potential overheating or damage.
Common Causes of A.O. Smith Code E1
- Faulty thermistor (inlet or outlet)
- Loose or corroded wiring connections to the thermistor(s)
- Damaged wiring harness leading to the thermistor(s)
- Control board failure
Applicable A.O. Smith Models
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Find a Licensed Tech Near You →Replacement Parts for A.O. Smith HVAC System Code E1
Inlet Thermistor OEM: 9005329005
Outlet Thermistor OEM: 9005329005
Control Board