A.O. Smith E6-50R45DV Water Heater Problems & Error Codes — Overview
The A.O. Smith E6-50R45DV is a residential electric water heater that uses an electronic thermostat with a red LED flash code system to signal faults. When something goes wrong, the red LED on the thermostat flashes a specific number of times to tell you whether the problem is a sensor, element, or control board issue. The most common complaints on this model and similar A.O. Smith electric units are failed thermistor sensors and heating element failures, both of which trigger distinct flash codes and require part replacement to restore normal operation.
This unit shares the diagnostic and repair pattern common across A.O. Smith’s electronic-thermostat electric heater line. The flash codes guide you directly to the failed component, whether it’s the upper or lower thermistor, the heating element circuit, or the electronic thermostat itself. Some units in this series also have an Energy Smart module that can fail and produce its own code. Most problems trace back to a handful of parts, and counting the red flashes is the first step in any repair.
Most Common Problems on This Model
- Red LED flashing for upper thermistor fault The upper temperature sensor has failed or lost connection, so replace the upper thermistor and check the wiring at the electronic thermostat.
- Red LED flashing for lower thermistor fault The lower sensor has failed or the connection is loose, so replace the lower thermistor and inspect the connector.
- Red LED flashing for element circuit fault A heating element is open, shorted, or the wiring is damaged, so check element resistance (should be 5–25 ohms) and replace the element if out of range.
- Red LED flashing for electronic thermostat fault The control board has an internal processor failure, so replace the electronic thermostat (ET).
- Red LED flashing for Energy Smart module fault (if equipped) The Energy Smart module has failed or lost communication, so inspect wiring and replace the ESM, then replace the ET if the code persists.
- No hot water and no flashing LED Power is off at the breaker or the electronic thermostat is completely dead, so check the breaker and replace the ET if no power reaches it.
- Intermittent heating or lukewarm water One heating element has failed but the other still works, so test both elements for 5–25 ohms and replace the bad one.
- Burned or melted wiring at element or thermostat Loose connections caused overheating, so replace damaged wiring and connectors, then tighten all element and thermostat terminals.
Parts That Commonly Fail
| Part | Notes |
|---|---|
| Upper thermistor sensor | Amazon | Fails and triggers upper sensor flash code |
| Lower thermistor sensor | Amazon | Fails and triggers lower sensor flash code |
| Heating element | Amazon | Burns out or goes out of 5–25 ohm range |
| Electronic thermostat (ET) | Amazon | Internal processor or circuit failure |
Water-Heater Error Codes for This Model
These codes apply to this model line:
- A O Smith Water Heater E2 error code
- A O Smith Water Heater E4 error code
- A O Smith Water Heater E6 error code
When to Call a Pro
Always turn off power at the breaker before opening any electric water heater panel. If you are not comfortable working with 240-volt wiring, testing element resistance with a multimeter, or matching flash codes to the service chart, call a licensed plumber or electrician. Any work that involves replacing the electronic thermostat, sensors, or elements requires disconnecting high-voltage wires, and incorrect wiring can cause a fire or shock hazard. If the flash code persists after you replace the obvious failed part, or if you see burned wiring or water inside the control cavity, stop and bring in a professional to prevent further damage or safety risk. For gas line, burner, or igniter work, or if you ever smell gas, stop and call a licensed technician.