Bosch Thermotechnology · Error codes
Buderus GB162 4C 224 — Safety Temperature Switch Measured an Excessively High Temperature and is Open, or no Connection Between Contacts 22 and 24 of the Uba 3 Mounting Base
4C 224
Safety temperature switch measured an excessively high temperature and is open, or no connection between contacts 22 and 24 of the UBA 3 mounting base. The safety temperature switch has measured an excessively high temperature and is open, or no connection is made between contacts 22 and 24 of the UBA 3 mounting base, depending on the boiler type which can have a safety temperature switch or that connection. The table classifies it as Locking fault code, reset required yes, UBA3 LED flashing at 1 Hz.
Applies to
This overheating code is displayed by the UBA3 control (display codes and LED flags) on Buderus GB162 models (80–200), as documented in Buderus GB162 Service Instructions, doc 6720614965_05 (6720614965_05). Codes can differ between controller generations, so always check the manual that matches your unit.
Controller: UBA3 control (display codes and LED flags). Source manual: 6720614965_05 (2012-11).
Why a code is not a diagnosis
An over-temperature code protects the heat exchanger or venting; it does not reveal whether the cause is low water flow, a failed pump, trapped air, fouling or a sensor fault.
Safe things to observe
- Note the code and whether rooms or hot water are still working.
- If you see steam, melted wiring or smell burning, switch the appliance off at its service switch and call a technician.
Do not
- Do not reset the appliance repeatedly while the cause is unknown.
- Do not remove covers or bypass any high-limit device.
How professional service helps
- A technician checks pump operation, flow, system pressure and the cleanliness of the heat exchanger.
- Combustion and safety devices are verified with an analyser and the manufacturer's procedure after any repair.
Where ROMA provides on-site service
On-site service is currently offered in Greater Vancouver, BC, including Vancouver, Burnaby, Richmond, Surrey, Coquitlam, North Vancouver, West Vancouver, New Westminster, Port Coquitlam, Port Moody, Delta, Langley, Maple Ridge, Abbotsford, Chilliwack, White Rock, Pitt Meadows, Tsawwassen, Anmore, Lions Bay, Belcarra, Bowen Island, Mission. Everything else on this site is reference information you can use anywhere in Canada.
Frequently asked questions
Can I clear this code myself?
Clearing a code without fixing its cause usually just brings it back. Note the code, check the safe items on this page, then call a licensed technician. If your appliance manual describes a user reset for this exact code and it stays away, no call may be needed.
Boiler locked out? Call with the alert text ready.
The brand, model and this alert are passed along when you request service online, so the technician arrives prepared.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.
Sources and verification
- Buderus GB162 Service Instructions, doc 6720614965_05 · 6720614965_05 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.