Laars Heating Systems · Error codes
Laars FT Series Wall 66 — Mixing Valve Initial Value Error (mixing Valve Cannot Return to Initial Position)
66
Mixing valve initial value error (mixing valve cannot return to initial position). The mixing valve cannot return to its initial position, so turn power off and on, check the wiring connections to the mixing valve, and replace the mixing valve.
Applies to
This domestic hot water fault code is displayed by the Laars FT wall control (NGTB-900CP) on FT Series Wall models (FTHW 100/140/199 heat-only and FTCW 140/199 combi), as documented in FT Series Wall Heat-Only Installation and Operation Instructions, Document 1483C (the FTCW combi manual 1487C prints the same code table) (1483C). Codes can differ between controller generations, so always check the manual that matches your unit.
- Laars Heating Systems FT Series Wall
- Laars FTHW100
- Laars FTHW140
- Laars FTHW199
- Laars FTCW140
- Laars FTCW199
Controller: Laars FT wall control (NGTB-900CP). Source manual: 1483C.
Why a code is not a diagnosis
A DHW code involves the hot-water side: sensors, flow, the mixing/bypass valve or the DHW heat exchanger. It does not say whether the fix is a sensor, a valve or a flush.
Safe things to observe
- Note the code and whether the problem follows a hot-water draw or appears at all times.
Do not
- Do not open the appliance to test DHW components yourself.
How professional service helps
- A technician tests the DHW sensors, flow switch and valve circuits, and cleans the DHW path where the manual directs.
- 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.
Parts and service
Parts commonly involved
These parts appear in the documented text for this alert. A code reports a condition, not a failed part — a technician confirms the cause by testing before anything is replaced.
Mixing valve (system temperature)
A mixing valve blends hot boiler water with cooler water so one boiler can serve parts of a system at different temperatures — warm floors,…
What a technician checks →
Service for this alert
- Gas Boiler Repair
Licensed gas technicians from ROMA Heating & Cooling diagnose and repair residential and light-commercial gas boilers across…
Every boiler part explained — what it does, how it fails and what a technician checks.
Documented for Laars Heating Systems FT Series Wall.
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
- FT Series Wall Heat-Only Installation and Operation Instructions, Document 1483C (the FTCW combi manual 1487C prints the same code table) · 1483C · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.