Bosch · Tankless water heater

E7 Control unit internal error

Medium severity Bosch Greentherm T9800 SEBosch Greentherm T9900 SE

What the control is telling you

Internal fault in the electronic control unit.

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

Likely causes

Control board failure

Test and repair steps

Hold the power button down roughly 3 s to clear the stored error.
Replace the electronic control unit if the error returns.

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

E1 Hot water above 194 F (90 C)
E3 Flue gas temperature too high, burner cut off
E4 Cabinet air too hot, burner cut off
E5 Condensing unit flue too hot, burner cut off
E8 Ionization test error
E9 Thermal fuse open
F2 Control unit internal error
F3 Control unit internal error / configuration

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Source: Bosch Greentherm T9800 SE 160/199 installation 6720816815 (06.2023), Table 24 Error code diagnostics, p.65-69; Bosch Greentherm T9900 SE 160/199 | i 199 installation 6 720 813 635 (2024-06), section 9.1 Error code diagnostics, p.68-73. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

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.