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Bosch · Tankless water heater

Error reset Hold ON/OFF key to clear an error code

Menu / mode display Bosch Greentherm T9800 SEBosch Greentherm T9900 SE

What the display is showing

Some faults clear after a reset. Holding the ON/OFF key for over 3 seconds clears an error code from the display; the appliance then starts its start-up sequence. If the error returns, contact a licensed professional.

Applies to: Greentherm T9800 SE 160/199 and T9900 SE 160/199 tankless water heaters

What to do

  1. Touch and hold the ON/OFF key for more than 3 seconds
  2. Wait for the start-up sequence

Models that show this code

6 models in Bosch Greentherm T9800 SE, Bosch Greentherm T9900 SE

Greentherm T9800 SE 160Greentherm T9800 SE 199Greentherm T9800 SEC 199Greentherm T9900 SE 160Greentherm T9900 SE 199Greentherm T9900 i 199

Other codes on the same units

  • EB Control unit internal error
  • EC Flame lost during operation
  • EE Gas valve modulation coil disconnected
  • EF Wrong gas type configured
  • FA Gas leak in the gas path
  • FC Touch key held over 20 seconds
  • FH FH failure history
  • HS HS about

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Source: Bosch Greentherm T9800 SE 160-199 installation 6720816815 (06.2023), 6.3 Error code reset p.45; T9900 SE 160-199 installation 6 720 813 635 (2024-06) same section. Summarized in our own words; check the original manual for your model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.