Weil-McLain AquaBalance F66 — Software Doesn't Match
F66
Software doesn't match. The software mismatch stops the boiler, and the device must be reprogrammed or replaced to restore normal operation again. The table classifies it as Soft Lock-out – Automatic Reset.
Applies to
This electronics fault code is displayed by the AquaBalance control (A##/F## fault codes) on AquaBalance Series 2 models (AB-80, AB-120, AB-155 and combi AB-80C, AB-120C, AB-155C), as documented in AquaBalance Series 2 Boiler Manual, doc 550-100-325/0924 (fault code tables 3 and 4) (550-100-325/0924). Codes can differ between controller generations, so always check the manual that matches your unit.
- Weil-McLain AquaBalance
- Weil-McLain AquaBalance AB-80C
- Weil-McLain AquaBalance AB-120C
- Weil-McLain AquaBalance AB-155C
- Weil-McLain AquaBalance AB-80H
- Weil-McLain AquaBalance AB-120H
- Weil-McLain AquaBalance AB-155H
Controller: AquaBalance control (A##/F## fault codes). Source manual: 550-100-325/0924 (2024-09).
Why a code is not a diagnosis
An electronics code points at the control board, memory or firmware. It is often triggered by poor incoming power or voltage backfeed from other wiring rather than by the appliance itself.
Safe things to observe
- Note the code and whether it appeared after electrical work or a power event.
Do not
- Do not open the control module.
- Do not repeatedly power-cycle to clear a recurring board code.
How professional service helps
- A technician checks supply voltage and grounding, follows the manual's reset sequence and replaces the module only if the code returns.
- 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
- AquaBalance Series 2 Boiler Manual, doc 550-100-325/0924 (fault code tables 3 and 4) · 550-100-325/0924 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.