Zehnder MVHR unit faults: fault codes, causes and parts
All 21 fault codes for Zehnder MVHR units, plus the faults that show no code. Type your code or choose your symptom.
A fault on an Zehnder MVHR unit usually means that the appliance has locked out or is reporting a fault code. Note the code on the display and look it up below: for each code you will find its meaning, checks you can safely do yourself and the parts that are often checked or replaced. Frequently searched: E1 (extract fan does not run), E2 (supply fan does not run), A3 (nTC sensor). No code? Check the power supply, the settings and the filters, and reset once. If the fault comes back, call in a qualified professional.
Most searched Zehnder faults
These are the codes that visitors to this site search for most often.
See the 25 most searched fault codes of 2026, with the figures behind them →
Zehnder MVHR unit faults without a code on the display
Not every fault shows a code. These are the symptoms we come across most often with Zehnder appliances, with what you can check yourself before calling someone out.
Filter message stays on
Replace the filters and then reset the counter on the control panel; without a reset the message stays on. Which filter set you need depends on the type and year of manufacture. View the matching parts → Read also: which MVHR filter set fits your unit →
Unit is noisier than before
Start with the filters: dirty filters make the fans run harder. If the noise persists, the fan bearings are often worn or there is dirt in the impeller. View the matching parts → Read the full explanation: MVHR unit making noise →
Draughts or cold air
In a properly working MVHR unit, the fresh air is preheated by the extracted air. If the supply air feels cold, the heat exchanger is dirty, the bypass is open or the pre-heater is faulty. View the matching parts → Read also: cold supply air – bypass or heat exchanger? →
Condensation or damp in the house
Usually the airflow is too low: dirty filters, a clogged duct or a unit stuck on the lowest setting. Have the air volumes measured if cleaning does not help. View the matching parts → Read also: which MVHR filter set fits your unit →
All 21 Zehnder MVHR unit fault codes
Order parts for your Zehnder MVHR unit
Zehnder parts are available from Instalpunt; shipping to EU countries from €12.95 (€16.95 for more distant countries), usually 3–5 working days.
Frequently asked questions about Zehnder faults
What does a fault on an Zehnder MVHR unit mean?
The appliance is reporting that it has shut itself down or cannot continue. The code on the display points to the group of causes: ignition, water pressure, a sensor, the fan or communication with the thermostat. The table above shows, for each code, what Zehnder means by it.
How do I reset my Zehnder MVHR unit?
The reset button is on the control panel of your Zehnder MVHR unit; on most appliances you hold it down for two to five seconds until the display responds. Reset once. If the same fault comes straight back, resetting will not solve it and a part or a setting needs attention. Always consult the manual for your model: the position of the button and how long to press it differ per series.
Can I fix a Zehnder fault myself?
You can top up the water pressure, bleed the system, replace filters and clean a siphon yourself. Anything behind the sealed section of a gas appliance is a different matter: work on the gas valve, burner, heat exchanger and flue must be carried out by a certified gas engineer.
How much does it cost to fix a fault?
That depends on the cause and whether a part is needed. With us you can see the part straight away with its price and delivery time, so you know where you stand in advance. If you call in an engineer, always ask about the call-out charge and hourly rate before they come.
Where can I find the right part for my Zehnder?
Check the rating plate for the exact type and use it to search our catalogue, or search directly by the manufacturer number of the faulty part. Each part lists the appliances it fits.