Low
S.O on Vaillant ecoTEC 65kW

Your boiler is working correctly but is currently in standby because it hasn't received a signal from your thermostat to turn the heating on.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Heating issue, no heat demand

From this model's manual
Verified against the Vaillant Ecotec 65kw installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This status occurs when the boiler is powered on and ready to work, but your internal controls have not told it to start heating. The most common reason is that your room thermostat is set lower than the current room temperature or the programmer/timer is currently in an 'off' period. It can also signify that the wireless connection between your thermostat and the boiler has been lost.

This is very common during the transition into autumn, when homeowners first try to use their heating but find the thermostat batteries have died over the summer.

DIY fix possible

Check that your room thermostat is turned up higher than the current room temperature.Ensure your heating programmer or app is set to an 'On' period.Replace the batteries in your wireless thermostat if the screen is blank or showing a low battery symbol.

Find a Gas Safe engineer
Search the official register →

Avoid the next call-out bill

A cover plan would handle faults like S.O: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Related fault codes

Related guides you might find useful