F.28 • Vaillant • aroTHERM
Vaillant fault code F.28: causes, diagnosis and solution
Fault code F.28 indicates a burner ignition failure after five initial attempts, causing the appliance to enter fault mode. This fault is also displayed if the problem persists after three manual reset attempts.
Proof status : Manufacturer reference needed for the exact range
Source: Vaillant documentation (service manual – according to product reference)
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Founder of AskMarcel.app. Sheets are written from manufacturer documentation; the reference is shown when it has been verified.
In brief
Fault code F.28 on Vaillant aroTHERM means: Fault code F.28 indicates a burner ignition failure after five initial attempts, causing the appliance to enter fault mode. This fault is also displayed if the problem persists after three manual reset attempts. Most common cause: The burner fails to ignite during the ignition attempt cycles as required by the appliance's safety logic. First action: Check that the gas shut-off valve is fully open.. Call a registered engineer if the fault returns after basic checks or involves refrigerant work (F-Gas registered engineer required).
According to Vaillant service documentation, code F.28 locks the appliance in fault mode after five failed ignition attempts.
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What does fault code F.28 on Vaillant mean?
Fault code F.28 indicates a burner ignition failure after five initial attempts, causing the appliance to enter fault mode. This fault is also displayed if the problem persists after three manual reset attempts.
The burner fails to ignite during the ignition attempt cycles as required by the appliance's safety logic.
Symptoms
- The burner does not ignite after five attempts.
- The appliance does not start and remains locked out.
- Fault code F.28 or F.29 is displayed on the screen.
- The appliance is in fault mode.
Diagnosis
1. Check the gas supply
- Check that the gas shut-off valve is fully open.
- Confirm that the fault is indicated by code F.28 or F.29.
2. Reset procedure
- Press the reset button to initiate an automatic ignition cycle.
- Monitor whether the problem is resolved after three reset attempts.
Repair and return to service — Vaillant fault F.28
If the gas shut-off valve is open, reset the appliance by pressing the reset button for one second. The appliance will attempt another ignition cycle. If the problem persists after three reset attempts, contact a qualified installer.
When should you call an F-Gas engineer?
Contact an F-Gas registered engineer if the fault returns after basic checks, involves refrigerant charging, or requires PCB or compressor replacement on Vaillant aroTHERM.
Affected models
- ecotec pro
- ecotec plus E
- ecotec plus systèmes E
- aroTHERM
- Vaillant
Field context
This code occurs during automatic ignition cycles or after a restart attempt following a fault. It indicates that the standard ignition sequence has failed five times, or that the safety system has locked the appliance after three unsuccessful manual resets, requiring
Frequently asked questions
What is the attempt threshold before code F.28 appears?
Code F.28 is displayed when the burner fails to ignite after five initial attempts, triggering fault mode. This code may also appear if the problem persists after three manual reset attempts performed by the user (Extract 1, Extract 2).
What is the reset procedure for code F.28?
Before resetting, check that the gas shut-off valve is fully open. Then press the reset button for one second to initiate an automatic ignition attempt. If the problem persists after three further attempts, contact an installer (Extract 1, Extract 2, Extract 3).
What should I do if code F.28 reappears after three resets?
If the ignition fault is not resolved after three manual reset attempts, the appliance must be referred to a qualified installer. The extracts explicitly state that the user should not continue reset attempts beyond this threshold without technical assistance (Extract 1, Extract 2, Extract 3).
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