Model compatibility has not been independently verified
Earlier archive data contained suggested model or series names. Without a clear model/code table in a manufacturer manual, these names are no longer displayed as verified matches.
This is general brand/device guidance; check the model label and official manual.
Open manufacturer sourceWhat does this code mean?
The Buderus manufacturer reference describes 4Y as heating flow temperature sensor fault. The code alone does not establish which component, if any, requires repair.
Buderus lists this error for the following product families: GB172i, GB062, GB012, GB072, GB042, U052, U062.
Read official manufacturer referenceWhat can you try safely?
Only follow steps approved for your specific model; stop if the fault indicates an unsafe condition.
- 01
Confirm model and error
Photograph the exact display code 4Y and read the complete model label. Buderus lists this error for the following product families: GB172i, GB062, GB012, GB072, GB042, U052, U062.
How to interpret the result: The precise model is essential.
- 02
Safe user check 1
Record whether the fault happened during heating or hot-water use. Do not disconnect sensors or open the casing.
How to interpret the result: Observe the result without opening internal assemblies.
- 03
Safe user check 2
After any permitted user check, observe whether the error recurs during normal operation; do not repeat lockout resets or open the unit.
How to interpret the result: Observe the result without opening internal assemblies.
- 04
Safe user check 3
Record when the issue began, any visible pressure or leak, and checks completed for a qualified technician. Ask which measurement supports any proposed repair.
How to interpret the result: Observe the result without opening internal assemblies.
How is the fault resolved?
User-accessible checks
- Record whether the fault happened during heating or hot-water use. Do not disconnect sensors or open the casing.
- After any permitted user check, observe whether the error recurs during normal operation; do not repeat lockout resets or open the unit.
- Record when the issue began, any visible pressure or leak, and checks completed for a qualified technician. Ask which measurement supports any proposed repair.
Professional diagnosis and repair
A technician compares sensor resistance/temperature values and checks continuity and connectors, replacing only a proven faulty part.
How to verify success: The error should no longer recur during normal operation. If it does, stop repeated attempts and request model-specific help.
Important: Never open gas-valve, combustion, flue or live-electrical assemblies. If you smell gas, do not operate electrical switches or appliance controls or create sparks. Leave the area safely and contact the local gas emergency service from outside. Unauthorized repairs may affect warranty coverage, depending on the applicable warranty terms and law.
Why can this happen?
The Buderus manufacturer reference describes 4Y as heating flow temperature sensor fault. The code alone does not establish which component, if any, requires repair.
- Manufacturer identifies a system condition, not necessarily a failed part.
- Model and operating circumstances affect the cause and proper repair.
Is this code valid for your appliance?
Buderus lists this error for the following product families: GB172i, GB062, GB012, GB072, GB042, U052, U062.