Bosch Error Code Fd: Reset button pressed by mistake (Boiler)
Bosch error code Fd on a boiler means: Reset button pressed by mistake. It is also called Bosch diagnostic code Fd.
Homeowner? What Bosch code Fd means for you
Usually minor Your boiler is reporting: Reset button pressed by mistake. This code is usually informational or minor. The safe checks below often clear it; call us if it keeps showing up.
Safe things you can check yourself
- Check the thermostat: right mode (Heat or Cool), set a few degrees past room temperature, and fresh batteries if it uses them.
- Make sure the unit has power: its on/off switch (often looks like a light switch near the unit) is ON and the breaker in the electrical panel is not tripped.
- Look at the pressure gauge on the boiler. If it reads much lower than usual or near zero, or water is leaking, call a technician.
- Outside, make sure the intake and exhaust pipes or vent cap are not blocked by snow, ice, leaves or a nest.
- Check that the boiler gas valve is open (handle in line with the pipe).
- Try one reset: turn the power off for 30 seconds, then back on. If the code comes back, stop resetting and call a technician.
Call (647) 657-2977Book a service call
Licensed technicians serving Vaughan, Toronto and the GTA.
What does Bosch error code Fd mean?
The reset button was pressed when no fault was set, or the harness shows a ground problem.
Applies to: Bosch Greenstar ZBR 21/28/35/42-3A boilers and ZWB 28/35/42-3A combi boilers
Common causes of Bosch code Fd
- Accidental reset press
- Ground fault in the harness to the safety high limit or gas cock
Bosch models that use code Fd
ZBR21-3AZBR28-3AZBR35-3AZBR42-3A
Other Bosch Boiler codes
| Code | Meaning |
|---|---|
| E9 | Safety high limit or flue gas limiter tripped |
| EA | No flame detected |
| F0 | Internal fault |
| F1 | Internal data error |
| F7 | Flame detected with burner off |
| FA | Flame detected after gas shut off |
All Bosch Boiler error codes →
Bosch code Fd: homeowner questions
What does Bosch code Fd mean?
Reset button pressed by mistake. The reset button was pressed when no fault was set, or the harness shows a ground problem.
Is it safe to keep using my boiler with code Fd?
Usually yes. Code Fd is normally minor, but if it keeps coming back have it checked.
Can I reset Bosch code Fd myself?
You can try one reset (power off for 30 seconds, then on). If Bosch code Fd comes back, the cause is still there and a licensed technician should check it.
Who can fix Bosch code Fd near me?
Aurora Star Tech Inc. repairs Bosch boilers in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.
Homeowner help: Boiler Not Heating: What to Check
Troubleshooting guides
- No heat or some zones cold All brands · Boiler
Source: Bosch Greenstar ZBR/ZWB 21-42-3A service manual 6721853955 (2025-11), Table 38 Faults shown on the display, p.74-75; Greenstar combi 100 p/151 p service manual 6721853953 (2025-11), Table 33. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.