F32 means your Vaillant has a problem with its fan, and it will not light until the fan is working and reporting the right speed. Some causes are as simple as a plug that has worked loose, others need a new fan or circuit board, and all of them are inside the casing.
What the fan does and why F32 stops the boiler
A condensing boiler like the ecoTEC uses a fan to draw in air, mix it with gas and push the burnt gases out through the flue. The boiler will not open the gas valve until it knows the fan is turning at the right speed, because without enough airflow the gas would not burn cleanly and the flue gases would not clear.
The fan reports its speed back to the control board through a small Hall sensor. If the board cannot see the fan, or the speed it reports is wrong, it stops and shows F32. Vaillant's ecoTEC plus installation and maintenance instructions (document 0020244997) list the code as "Fault: Fan", with the cause "Fan defective or not connected". The ecoTEC pro manual (document 0020244995) uses the same wording.
The causes listed in Vaillant's manuals
The LPG ecoTEC plus manual (document 0020239015) breaks the cause down further. Grouped from the quickest to check to the most expensive, the list looks like this:
Connection problems
The plug on the fan not seated properly, the multi-pin plug on the circuit board not pushed fully home, or a break in the cable harness between them. These are common after a service or repair where the fan or board was disturbed, and the fix is often just reseating or repairing a connection.
A blocked fan
Debris or a seized bearing can stop the fan spinning freely. A fan that has been getting louder, whining or rattling for a while before F32 appeared fits this cause.
A failed Hall sensor
The fan may be spinning, but if the speed sensor has failed the board still cannot see it. To the homeowner this looks the same as a dead fan.
Defective electronics
Either the fan's own electronics or the control board that drives it. This is the least likely cause and the last one an engineer will settle on, after the plugs, wiring and fan have been ruled out.
| Cause | Possible clue | Usual repair |
|---|---|---|
| Loose fan or board plug | F32 began soon after a service or repair | Reseat the connection |
| Broken harness | F32 comes and goes | Repair or replace the cable |
| Fan blocked or worn | Whining or rattling before the fault | New fan |
| Hall sensor failed | Fan noise but still F32 | Usually a new fan |
| Electronics defective | Everything else checks out | New fan or circuit board |
A different description on 2021 open-vent models
If you own a regular open-vent ecoTEC plus VU ../6-5 OVZ, the 2021 manual (document 0020238195) words F32 differently: "Fan frost protection function active: Fan speed outside the tolerance values". The underlying problem is the same, the fan speed is not where it should be, but the wording shows that on these boilers the code sits alongside the fan's frost protection function. If you have this model, quote both the code and the wording on the display when you book the repair.
What you can check without opening the boiler
- Reset the boiler once. Vaillant's 2021 and LPG manuals say to press and hold the reset button for more than three seconds.
- Listen as it restarts. Note whether you hear the fan run up, hear nothing at all, or hear a grinding or whining sound. That detail helps the engineer more than you might expect.
- Think back to when F32 first appeared. A recent service, a repair, a power cut or a storm are all worth mentioning.
- If F32 returns after two or three resets, leave the boiler off. Do not keep switching it off and on at the fused spur to force a restart.
Never remove the casing to check the fan plug or spin the fan by hand. The fan sits next to the gas valve and burner and is wired at mains voltage. Leave it to a Gas Safe registered engineer.
What the repair involves
The engineer will start with the cheap and simple checks: the fan plug, the board plug and the harness. If those are sound, they will test whether the fan is getting power and whether it is reporting speed. A seized fan, a failed Hall sensor or worn bearings all mean a new fan, which is a common repair on boilers of a certain age. A replacement circuit board is only needed if the fault is traced to the board's fan output.
A fan is a gas-related part, because it controls the air and gas mixture, so after replacing it the engineer should check the combustion is right before leaving.
Typical repair costs in the UK
| Job | Typical UK cost |
|---|---|
| Engineer call-out and diagnosis | Typically £60 to £150 |
| Reseating a plug or repairing the harness | Typically £100 to £180 |
| Fan replacement | Typically £200 to £400 |
| PCB replacement, fitted | Typically £250 to £550 |
Our boiler fan replacement cost guide explains what affects the price of a new fan, and the PCB replacement cost guide covers the rarer board fault. If your ecoTEC is well past its warranty and also has other faults, our guide to whether to repair or replace a boiler may help you weigh it up.