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Viessmann Boiler Fault Codes
What the code on the display actually means, what usually causes it, and what you can safely check before calling.
A Viessmann boiler locks out and shows a code when one of its safety checks fails. The code is genuinely useful information, so write it down before you reset anything. Below are the codes we are called out for most often on the South Shore, each with what the boiler is reporting and what a plumber actually finds behind it.
Temperature limiter has tripped — the boiler shut down on over-temperature.
No flame signal — the boiler tried to light and could not confirm a flame.
Air pressure switch or fan fault — the boiler cannot confirm safe air flow.
Flue gas over-temperature — exhaust temperature exceeded its safe maximum.
Flame signal fault during start-up — the flame was lost or never stabilised at ignition.
Not the code you are seeing? Call us with the exact characters on the display and we will tell you what it means. For servicing and repair generally, see Viessmann boiler service or boiler repair.
Boiler locked out and showing a code?
Book online and we will diagnose the actual cause rather than clearing the code and hoping.
Viessmann fault code FAQs
Where do I find the fault code on a Viessmann boiler?
On Vitodens models the code shows on the control panel display, usually alongside a red indicator. Note the exact characters before resetting, because the code is the fastest route to the right diagnosis and it disappears once cleared.
Is it safe to reset a Viessmann fault code?
One reset is reasonable for most codes. What is not reasonable is resetting repeatedly. These codes come from safety devices, and a boiler that keeps locking out is reporting a real condition that resetting does not change.
Why do so many Viessmann faults happen in cold weather?
Condensing boilers drain acidic condensate continuously. On the South Shore that pipe often runs through an unheated basement or outside, and a hard freeze blocks it. A blocked condensate route is behind a large share of winter lockouts.
Do you service Viessmann boilers you did not install?
Yes. We diagnose and repair Viessmann equipment regardless of who installed it, and we tell you plainly when a repair is the right call and when replacement is the more honest answer.
Why South Shore homeowners choose Johnson Bros.
Viessmann boiler fault diagnosed properly
We read what the boiler is telling us, find the cause, and give you an upfront price before any work starts.
Not sure what's wrong? Send a photo or videoBooking online is the quickest way to hold the next open appointment. Call instead if it is urgent and you would rather talk to someone.
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Viessmann boiler fault diagnosed properly
We read what the boiler is telling us, find the cause, and give you an upfront price before any work starts.
Call for urgent help now. Book online when you want the next available fit for your schedule.