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Baxi error code E133 – ignition lockout

posted on 11 Jan 2020

E133 error code on a Baxi/ Potterton / Main boiler is an ignition lockout fault code. This error code that covers a wide range of possible faults connected to gas and igniton. In most cases you will need to contact a competent boiler repair engineer but there are some steps you can take yourself before booking a repair:

  • check if gas supply is turned on – if you have a gas hob see if there is gas coming to the gas hob. You can also check if your gas meter ECV (Emerngecy Control Valve) is turned on parrarel to the pipework
  • check if your meter has credit (Pre paid meters only)
  • if outside temperatures are below zero – check if condensate pipework is frozen. If it is pour hot water over the pipework.
  • check if your condensate pipework is not blocked

If above steps did not help you will need to book a professional reapir. E133 error codes can be split into 2 groups (provdied that the error is not caused by lack of gas or frozen or blocked condensate pipework). First group is when boiler does not ignite at all. (Flame led does not illuminate and there is no flame visible in the sight glass) Possible causes in this case are:

  • faulty gas valve
  • faulty wiring between gas valve and PCB
  • faulty PCB
  • faulty ignition module
  • faulty igntion electrodes
  • gas valve out of calibration – wrong mixture of air/gas

Second group of E133 error codes happens when boiler does ignite (flame led illumiates for a short period and flame is visible in the sight glass) – but goes out shortly after. In this case list of possible faults is shorter as we know that the gas valve opens and that igntion module is working fine. List of possible faults is as follows:

  • gas valve out of calibration – wrong mixture
  • sensing electrode faulty out of alignment
  • sensing electrode wiring
  • PCB

Below you can see a video of a E133 Baxi Duo Tec boiler under fault condition. In this case the boiler would not fire up at all.

The pump and fan would come on at full speed and there would be audible click / clang noise.The noise would happen exactly 3 times and then boiler would go to E133 error code. You can clearly hear the ‘clang’ noise in the video below. The noise was coming from the gas valve. After testing spark generator and confirming it was working fine I tested gas valve coil resistance. The resistance was in norm. However I suspected it was the gas valve not opening as it was making a rather unhealthy nosies. I also did not have apressure drop on gas valve test point – meaning that the gas valve was not opening at all. Have a listen to the gas valve ‘clang’ noise when it tries to open but fails.

In this particular case the gas valve was faulty although the coil resistance was in norm. They require to be set up with a gas analasyer as they come unadjusted from the factory. After repair and careful setting up boiler is working happily again. (See video below)

If your boiler suffers from E133 fault and you are based in in my area (see my web site ‘Areas Covered’ for details) please get in touch here gas engineer in Crystal Palace