Common problems guide

The most common Vaillant Turbomax Pro 28 2E problems

The faults most likely to send a Vaillant Turbomax Pro 28 2E into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

This model is discontinued. Parts can be harder to source and expensive. If repair costs are mounting, a new A-rated boiler may be the smarter choice.
18 documented codes
6 most common
0 DIY-safe checks
6 engineer needed

The 6 most common faults

01
1F High Engineer

Your boiler has suffered a major electrical failure where the internal fuse blows instantly, meaning the main control board has likely short-circuited and stopped working.

Why it happens: This fault occurs when a component inside the boiler fails and draws too much electricity, causing the internal fuse to blow instantly to protect the system. The most common reason is a short circuit within the main control board itself or a failed internal pump that has suffered an electrical surge.

Est. cost
£250-£450
Parts
Main Printed Circuit Board (PCB), Internal Fuse
Full guide for 1F
02
Er.1 High Engineer

Your boiler has failed to ignite the gas needed to heat your home, which has triggered a safety shutdown.

Est. cost
£120-250
Parts
Ignition lead, Ignition electrode, Gas valve
Full guide for Er.1
03
Er.2 High Engineer

Your boiler is failing to light the burner because it cannot detect a flame or spark, meaning you currently have no heating or hot water.

Est. cost
£120-250
Parts
Ignition lead, Ignition electrode, Printed Circuit Board (PCB)
Full guide for Er.2
04
Er.3 High Engineer

Your boiler has detected an issue with the internal ventilation system that removes exhaust gases, so it has automatically stopped working to keep your home safe.

Est. cost
£180-350
Parts
Fan assembly, Printed Circuit Board (PCB), Wiring harness
Full guide for Er.3
05
Er.5 High Engineer

Your boiler's temperature sensor is providing an incorrect reading or has disconnected, which prevents the system from safely heating your water.

Est. cost
£120-200
Parts
NTC Temperature Sensor, Wiring harness
Full guide for Er.5
06
Er.6 High Engineer

Your boiler has detected that the water temperature is rising too quickly or overheating, suggesting that internal parts are struggling to move heat away from the burner efficiently.

Est. cost
£250-500
Parts
Primary heat exchanger, NTC thermistor, Pump
Full guide for Er.6
Parts most often replaced

on the Vaillant Turbomax Pro 28 2E

Main Printed Circuit Board (PCB)Internal FuseIgnition leadIgnition electrodeGas valvePrinted Circuit Board (PCB)

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

  • You can smell gas or see signs of a leak
  • The Vaillant shows an Emergency or High severity code
  • The boiler keeps locking out after repeated resets
  • You've tried the DIY checks and the fault hasn't cleared
  • There's visible water leaking from the boiler
  • The flame is yellow or orange instead of blue
See the full 18-code list for the Vaillant Turbomax Pro 28 2E

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →