Potterton [E128] fault codewhat it means and how to fix it

E128 is loss of flame, logged when the appliance lights successfully and then loses the flame signal during operation. Potterton documentation describes it as flame failure occurring repeatedly — some sources give twelve occurrences as the threshold before it latches. The distinction from an ignition lockout is the useful part. If the burner lit, then the electrode sparked well enough, gas arrived, and the valve opened. Something interrupted a flame that was already burning. In practice there are four realistic explanations: the gas supply sags under load rather than being absent, condensate backs up shortly after firing, the flue recirculates its own products once warm, or the sensing electrode loses a marginal signal as the combustion chamber heats up and components expand. Wind across an exposed flue terminal belongs on the list too, and on the flats and end-terrace properties where Promax appliances often sit, exposed terminals are not unusual.

1. 1

   Keep a short log over a few days: what time it failed, what else was running in the house, and what the weather was doing. E128 is a pattern fault, and the pattern is most of the diagnosis.

2. 2

   Pay particular attention to whether it drops out at the same point every single time. A stopwatch-consistent failure two or three minutes in is the signature of condensate backing up internally.

3. 3

   Run it once with every other gas appliance off, then once with the hob going flat out. A clear difference between those two tells an engineer to arrive with a manometer.

4. 4

   Hand the log over when somebody attends. An intermittent fault that refuses to perform on the day is the most expensive kind to chase, and your notes are what stops it taking three visits.