Vaillant F.325 fault codewhat it means and how to fix it
The 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.
Take care
Get a Gas Safe registered engineer to look at your Vaillant F.325
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.325 means
The ecoTEC plus CS/1-5 gives its pump a family of codes, and F.325 is the general one: "the heating pump has a fault — pump blocked: check that the pump is working correctly; the pump is defective: check and, if required, replace the pump". Around it sit four more specific rows with the same remedy and the same part. F.320 is "the heating pump is blocked; the unlocking function was not successful — dirt or foreign bodies in the pump: clean the pump and, if required, replace the pump", the CS/1-5 having first tried to free a stuck rotor on its own.
F.321 is "the pump electronics are defective — the pump is defective: check and, if required, replace". F.324 is "the electrical connection to the pump has been interrupted — the cable to the pump is defective: check the cable for the 230 V power supply to the pump and, if required, replace it; the pump is defective". F.330 is "the pump is not responding to commands during the hydraulic test — fault in the electrical connection for the pump: check the wiring harness between the PCB and pump; the pump is defective".
Read together, the family says the same thing five ways: the board has lost confidence in the pump, either because it will not turn, will not answer, or is not wired to it, and Vaillant's remedy at every step is to check the pump and its connections and replace it if required. The two rows that stand apart are F.322 (overheated) and F.323 (dry running), which have pages of their own because their causes reach beyond the pump. None of these codes exists on a two-digit Vaillant, whose pumps are not monitored this way.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Pump blocked by dirt or debris | F.320's cause and F.325's first. Sludge or a foreign body has stopped the rotor, and the CS/1-5's automatic unlocking could not free it. | Common |
| Pump defective | The pump itself, named on every row in the family. Includes F.321's "pump electronics are defective". | Common |
| 230 V supply cable to the pump | F.324's cause. A damaged or disconnected power lead leaves the pump silent, and the board reports the connection interrupted. | Occasional |
| Control harness between PCB and pump | F.330's cause. The pump has power but does not respond to the board's commands during the hydraulic test, which points at the signal lead. | Occasional |
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
A cable or connector repair is a call-out of £80 to £150. A pump is £250 to £320 fitted; a system clean is extra if the pump was blocked by sludge.
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
Magnetic system filter, 22mm
MAG-22£65–£120Plumbing merchant
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.89Get it checkedThe 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.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.325
Which code do I actually have, and does it matter?
It tells the engineer where to start: F.320 at the rotor, F.324 at the power lead, F.330 at the control lead, F.321 and F.325 at the pump itself. For you the answer is the same — a Gas Safe engineer and, quite possibly, a pump.
Can I free a blocked pump myself?
No. On the CS/1-5 the pump is inside the sealed case and the boiler has already tried its own unlocking routine. Older boilers had a bleed screw you could turn a rotor with; this one does not offer that to the householder.
Why did it happen?
Blockages come from a dirty system, so if a pump has failed for that reason, ask about a system flush and a magnetic filter, or the replacement will go the same way.
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.