Vaillant F.89 fault codewhat it means and how to fix it
The pump is not connected, is connected incorrectly, or is not the pump the boiler expects. On the 2022 CS/1-5, F.089 means the fitted pump does not match the unit type.
Take care
Get a Gas Safe registered engineer to look at your Vaillant F.89
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What F.89 means
F.89 is the pump's connection check, and the one of the three that most often points at a replacement part rather than a loose plug. The ecoFIT pure, ecoFIT sustain and ecoTEC sustain print it as "fault: pump — pump not connected or connected incorrectly, incorrect pump connected, short circuit in the cable harness", and the open-vent ecoTEC plus titles the row "incorrect pump detected" and expands the middle cause into an unsuitable pump, a PWM plug that is loose or off, the board's multiple plug, the harness and the electronics.
The 2022 CS/1-5 drops the wiring causes altogether and makes F.089 purely about the part — "the installed heating pump does not match the unit type — check whether the pump that is connected is the one recommended for the product". Modern Vaillant pumps are modulating, controlled over a PWM signal lead as well as powered, and the board recognises the pump it is talking to.
A pump of the wrong type, a generic replacement, or a pump with its PWM lead unplugged all fail that recognition. So F.89 arrives in two situations: straight after a pump change, when the wrong pump or a missed lead is the answer, or with no recent work, when a plug or harness has failed. Not a row on the ecoTEC plus ..6/5-5, pro or exclusive.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Wrong pump fitted | Vaillant's "incorrect pump connected", and the only cause on the CS/1-5. A replacement pump that is not the type specified for the model is not recognised by the board. | Common |
| PWM control lead unplugged | The open-vent table's "PWM plug not plugged in or has come loose". The pump has power but no control signal, and the board reports it as not connected. | Common |
| Multiple plug on the PCB or harness fault | The board-end connector not seated, or a short or break in the pump harness. Named on the ecoFIT, sustain and open-vent rows. | Occasional |
| Electronics defective | Last on the open-vent list. The pump control output on the board has failed. | Rare |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£80–£320
Time on site
1 hour
Reconnecting a lead is a call-out of £80 to £120. If a pump has to be replaced with the correct type, £250 to £320 fitted.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Central heating circulating pump
CH-PUMP-15-60£90–£180Plumbing merchant
Price checked 28 September 2026
Vaillant wiring harness (plug-and-cable set to a sensor or actuator)
£20–£65Authorised Vaillant parts distributor
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Vaillant fault codes
- F.325Get it checkedThe heating pump in a 2022 ecoTEC plus has reported a fault — blocked, or defective. F.320, F.321, F.324 and F.330 are its neighbours in the same pump family, and this page covers them too.Related: pump and hydraulics
- F.323Get it checkedThe heating pump in a 2022 ecoTEC plus is dry running — turning with no water in it. Vaillant name air in the boiler as the cause; a pump run dry may need replacing.Related: pump and hydraulics
- F.322Get it checkedThe heating pump in a 2022 ecoTEC plus has overheated, and running it more gently did not bring the temperature down. Vaillant's remedy is to check and if necessary replace the pump.Related: pump and hydraulics
- F.94Get it checkedThe vortex and differential pressure sensors — the two that measure flow through the heat exchanger on an ecoTEC plus or exclusive — are returning values the board does not believe.Related: pump and hydraulics
- F.22Get it checkedThe boiler has shut down because there is not enough water in the system. Pressure has dropped below roughly 0.5 bar and it will not fire until you top it up.Related: same brand
- F.75Get it checkedThe boiler cannot detect a rise in pressure when the pump starts, so it has locked out. Usually a failed pressure sensor or a pump that is not moving water.Related: same brand
Own a Vaillant boiler? Save it and its codes come first next time.
Related guides
Common questions about Vaillant F.89
The pump was replaced last week. Is that the cause?
Very likely. F.89 after a pump change means either the wrong pump or a control lead not reconnected. Vaillant's instruction on the CS/1-5 is to check the pump is the one recommended for the product; the fitting engineer should return.
Is the boiler safe to leave on?
Yes. Without a recognised pump the board will not fire the burner, so there is no risk of the heat exchanger running without circulation. The display and frost protection stay active.
Can a non-Vaillant pump be used?
Only one the board recognises, and Vaillant's table says to fit the pump recommended for the product. A generic pump that the board rejects gives F.89 every time.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.