Installation Guide
(ESM)
ERROR 
CODE
(ET)
DIAGNOSTIC 
LED
INDICATES CORRECTIVE ACTION*
LIGHT ON
(Green Flash)
Normal operation. None
NO LIGHT No electrical power to control board
or diagnostic LED light burned out.
1. Check for blown fuses or tripped breaker.
2. If diagnostic LED light is burned out, replace Electronic Thermostat 
 (ET).
E01
1 FLASH
(Red)
Dry-fire, electrical power on with the 
tank not completely full of water.
1. Turn off electrical power at breaker, add water. 
2. Turn on electrical power at breaker.
3. See “Important Safety Information” on page 4.
E02
2 FLASHES
(Red)
Water temperature exceeded high 
limit.
1. Turn off electrical power at the breaker.
2. Press the reset button (see Figure 9).
3. Turn on electrical power at breaker.
4. If error returns call a service technician for assistance.
E03
3 FLASHES
(Red)
Upper thermistor sensor failure.
(Note: Upper thermistor sensor is
part of the ET)
1. Turn off electrical power at the breaker.
2. Replace Electronic Thermostat (ET).
3. Turn on electrical power at breaker.
E04
4 FLASHES
(Red)
Upper element circuit failure.
(Note: Lower element is still operable)
1. Turn off electrical power at the breaker.
2. Check element circuits for resistance of 5-25 ohms (replace if required).
3. Check wires at elements and Electronic Thermostat (ET) for damage. 
 If this 4 flashes condition continues, replace Electronic Thermostat (ET).
4. Turn on electrical power at breaker. 
E05
5 FLASHES
(Red)
Lower element circuit failure.
(Note: Upper element is still operable)
1. Turn off electrical power at the breaker.
2. Check element circuits for resistance of 5-25 ohms (replace if required).
3. Check wires at elements and Electronic Thermostat (ET) for damage.
 If this 5 flashes condition continues, replace Electronic Thermostat (ET).
4. Turn on electrical power at breaker.
E06
6 FLASHES
(Red)
Electronic Thermostat (ET) failure
(Internal processor).
1. Turn off electrical power at the breaker. Now turn on electrical power to 
 see if error clears. If error has not cleared, replace Electronic Thermo-
 stat (ET).
2. Turn on electrical power at breaker.
E07
7 FLASHES
(Red)
Lower thermistor sensor failure. 1.  Turn off electrical power at the breaker.
2. Check electrical connections at Electronic Thermostat (ET).
3. Replace Lower Thermistor Sensor.
4. Turn on electrical power at breaker.
E08
8 FLASHES
(Red)
Energy Smart
®
 Module (ESM)
failure.
1. Turn off electrical power. 
2. Check wires at the interface module for damage.
3. If this 8 flashes condition continues, replace module (ESM).
4. See “Overriding The Interface Module (ESM)” by unplugging from the 
 Electronic Thermostat (ET) on page 18. NOTE: Electronic Thermostat 
 (ET) will continue to be operate, hot water will still be available.
5. Turn on electrical power at breaker.
Setpoint
Knob
Diagnostic
LED Light
Plastic Guard
IMPORTANT: Before attempting to adjust the ther-
mostat, read the “Important Safety Information” 
section page 4. 
The Electronic Thermostat (ET) is designed so 
that it may control the water heater without the 
Energy Smart
®
 Module (ESM) being operated, 
see page 18.
If the instructions are not clear, contact a qualifi ed 
person.
DIAGNOSTIC CODE CHART Electronic Thermostat (ET)
 22 • Residen al Electric Water Heater Use and Care Guide
TROUBLESHOOTING
WARNING! Electrical Shock Hazard
Do not remove the plas c guard from 
over wiring.
Do not touch electrical wiring.
Failure to do so can result in death or 
electrical shock.










