Problem wth the good old Icos M3080 (not firing up)

[pergolies]

Boiler wont fire up and getting the flashing L F code. Seems a coincidence that it started playing up after draining the hot water system to change some taps. Not sure if or why this would affect the boiler.

One thing to note is that the central heating pump is constantly running, unless i turn the power of to the whole system or slide the switches on the control panel to off position on both the hot water and heating (dont think that right somehow)

Now, firstly the things i've tried and tested for.
1. opened up drain plug on bottom of sump to check for any air in system (none)
2. Checked the ignition electrode for continuity, wasn't happy with it (but that might of been my tester playing up) so replaced it with new one.
3. Checked voltage to gas valve. When the boiler goes through its start up process i get around 200 volts for about a second then goes to to 0 volts. As per the manuals trouble shooting it says change the gas valve. New gas valve fitted (still nothing)
4. Read somewhere to disconnected the live feed at L2 terminal on mains wiring coming into boiler to check if its the boiler or an external fault. If the boiler powers up and gives the reading '0' then its an external fault (so they say). Well boiler powers up and reads '0' on the display.
5. Checked to see if i get a spark at the ignition electrode by disconnecting it from burner and earthing, then covering hole to stop gas escaping. Get no spark or a voltage reading at terminal. Not sure if this is normal if there is a fault elsewhere or its a fault with the PCB!!!

Would appreciate any input before i start spending anymore money (which i haven't got at mo)

Cheers

 

[Agile]

You will waste a lot of money if you blindly change parts!

Was the person who changed the gas valve CORGI registered?

I am trying to find a similar fault on one at the moment but it works fine when I am there but the tenant says it never works after I leave!

Tony

 

[weareleeds]

Has burner been removed to check if earth pin kit has been fitted? If this is missing it can cause flashing l-f also insulation boards may have dropped down which will cause the combustion box to burn out

 

[shambolic]

Sounds more like the sensing pipe blocked this will cause the governor to fail to lift. Especially on the old M series as the wee screw its onto is level with bottom of combustion chamber and any water and garbage will fall in.
Also make sure the pipe is connected to the wee hollow chrome screw and not the one next to it as ..I....sorry one of my engineers did this recently after fitting a gas valve and thought the new one was faulty....It was a long day OK
Sorry read yer post again so no spark at electrode on the old M board the spark comes straight off the board disconnect it at that side and earth it will insulated pliers to see if spark.

Ps why did you not just turn off the gas when checking if sparking rather than "finger over the hole"???

 

[BGEngineer]

Funny you should say that about the impulse tube shambolic, I went to one today, where a colleague of mine had changed the gas valve and put the tube on the threaded stud rather than the nipple. Numerous visits later due to intermittent LF the manufacturers were called in and even they missed it, this was all back in June! The poor woman has been putting up with it since then. Even when I went round tonight it was doing it before I found the fault, shocking.

Any LF fault now Im taking the burner out, One of my colleagues is going through a disciplinary for missing a hole in the burner housing.

 

[gas4you]

a hole in the burner housing.

Surely this would show up as high CO when testing with an FGA?

 

[BGEngineer]

Most definately, but would only fire up with the case off. The boiler wasn't left in operation and it was our own manager who spoted it and instigated the disciplinary, bit harsh as the guy asked him to come round for some tech advice, but thats BG for you.