Bosch · Water Heater
Bosch Therm 250SX, GWH 635ES and 2400E gas tankless error codes
Bosch Therm 250SX, GWH 635ES and 2400E gas tankless codes. 16 codes.
Check this is your model before you read on
The model number on your data plate should start with 250SX, 635ES, 2400E. These are letter and number pairs, not numbers, so there is no counting step. Reset is a button on the unit, and a reset only clears the code if the condition behind it has gone away, which is why a code that immediately returns is a finding in itself.
Condensing gas tankless platform with a condensing heat exchanger, an induction fan and a flue gas limiter. Four of its codes, A2, A7, A9 and C1, mean something completely different on the Greentherm T9000 platform, and the gas pressure ranges published for it differ from the T9000 ranges, so the code has to be read against the model family rather than as a Bosch code.
How to read this code
These heaters show a two character code on the display and the same code can mean two completely different things on a different Bosch platform, so check which model family the code belongs to before you act on it. A2 on this platform is an overheat protection trip, while A2 on the Greentherm T9000 means an external temperature sensor is not detected. The same goes for A7, A9 and C1. Codes starting with E are usually combustion or sensor faults that stop the burner, and codes starting with F point at flame sensing and the gas valve. C codes are the fan and water flow checks.
16 codes on this control platform.
16 fault codes
Every one of these means something is wrong. Ordered by how urgent they are.