A. O. Smith · Voltex hybrid with letter codes (HPTU, 2016–2019)
A. O. Smith Voltex hybrid with letter codes (HPTU, 2016–2019) error code ECF
Compressor short cycling
What it means
The heat pump compressor is starting/stopping frequently.
How it shows: may have an audible alarm; to cancel the audible alarm, press any button on the UIM
What A. O. Smith says to do
1. If compressor is running and fan is not operating, call residential technical support. 2. Clean the air filter (see "Air Filter Maintenance"). 3. Check installation location against recommended confined space requirements.
Last checked 2026-10-03.
Safety first
- WARNING! Electric Shock Hazard; Disconnect power before servicing. Do not remove the plastic guard from over wiring. Do not touch electrical wiring. Failure to do so can result in death or electrical shock. (diagnostic code pages, p.20-21)
- WARNING! Working near an energized circuit can result in severe injury or death from electrical shock. WARNING! When you are finished, be sure all covers are secured to reduce the risk of fire and electric shock. (p.22)
From the manufacturer's manual for this series.
The same code on other models
Codes mean different things on different heaters. Match the series to the model number on your rating label.
Other Voltex hybrid with letter codes (HPTU, 2016–2019) codes
- - / -- / --- (System diagnostic)
- ICE (Defrost)
- HPO (Out of operating range)
- EUC (Upper element)
- ELC (Lower element)
- SF (Air filter)
- E20 or E21 (Upper temperature sensor)
- E30 or E31 (Lower temperature sensor)
- E50 or E51 (Suction temperature sensor)
- E10 or E11 (Coil temperature sensor)
- E40 or E41 (Discharge temperature sensor)
- E60 (Upper and lower sensors)
- Edr (Dry fire / tank not full)
- EPL (Low supply voltage)
- EDH (Discharge temperature high)
- EoF (Condensate management)
- ECL (Suction pressure low)
- EEE (EEPROM failure)
- ECC (Compressor not functioning)
- ECE (Power supply error)