Bosch · Tankless water heater

Display blank Display blank - appliance off

Normal status Bosch Greentherm T9800 SEBosch Greentherm T9900 SE

What the display is showing

After the ON/OFF touch key is held for more than 3 seconds the appliance turns off and the display goes blank. Holding it again for more than 3 seconds turns the appliance on and the display shows the selected temperature. A blank display with the appliance expected on points to a power supply check.

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

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

CA Water flow above 9.2 gpm
CE Flue blockage during operation (siphon pressure)
CF Flue blockage during operation (insufficient air)
DH DH data history
EA Ignition failure
EB Control unit internal error
EC Flame lost during operation
EE Gas valve modulation coil disconnected

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Source: Bosch Greentherm T9800 SE 160-199 installation 6720816815 (06.2023), 6.2 Power p.45 and 7 Maintenance - descaling steps; 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.