Weil-McLain CGi DHW VOLTAGE HIGH — DHW / Thermostat2 Input Excessive Voltage
DHW VOLTAGE HIGH
DHW / Thermostat2 input excessive voltage. The DHW/Thermostat2 input has excessive voltage, so the supply voltage must be measured between control connector pins 4 and 6.
Applies to
This domestic hot water fault code is displayed by the CGi control (display messages) on CGi Series 5 models (CGi-25 through CGi-8), as documented in CGi Series 5 Boiler Manual, doc 550-100-629/0126 (550-100-629/0126). Codes can differ between controller generations, so always check the manual that matches your unit.
- Weil-McLain CGi (cast iron)
- Weil-McLain CGi-25
- Weil-McLain CGi-3
- Weil-McLain CGi-4
- Weil-McLain CGi-5
- Weil-McLain CGi-6
- Weil-McLain CGi-7
- Weil-McLain CGi-8
Controller: CGi control (display messages). Source manual: 550-100-629/0126 (2026-01).
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.
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
- CGi Series 5 Boiler Manual, doc 550-100-629/0126 · 550-100-629/0126 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.