Vaillant ecotec pro 28 f28

[Hobo128]

Been out to this boiler tonight. Open hot or ch demand boiler fires up for about 2 - 3 seconds and then goes off, repeats its self about 4 more times the locks out with f28.

Ive checked the gas valve for resistance.

Checked continuity of gas valve leads.

Check earth to boiler.

Took out spark electrode which is sparking and checked inside burner which is squeeky clean, also condense is not blocked. Fan runs and pump runs.

Any ideas

 

[Chalked]

Could be gas valve.
Is it in warranty?

 

[Scott_D]

Inlet pressure good?
Flame rectification?

 

[Harvest Fields]

Does it make any noises once alight?

 

[Hobo128]

It doesnt make any noises when alight. Inlet pressure 20mb.
Is there a way to check flame rectification?

 

[Harvest Fields]

It doesnt make any noises when alight. Inlet pressure 20mb.
Is there a way to check flame rectification?

What does the pressure drop down to when you run P1?

 

[ShaunCorbs]

sounds like its not sensing a flame i would say probes

give them a clean with some sandpaper

 

[Harvest Fields]

sounds like its not sensing a flame i would say probes

give them a clean with some sandpaper

Could be. But I would also check the working at the valve. Had a faulty regulator before Christmas and when the boiler was on full power was only giving about 6mbar.

 

[ShaunCorbs]

Could be. But I would also check the working at the valve. Had a faulty regulator before Christmas and when the boiler was on full power was only giving about 6mbar.

faulty gov? or was it the gas valve

 

[Harvest Fields]

faulty gov? or was it the gas valve

Neither. Have no idea why I typed that. It was a blockage in the mains. I thought it was a faulty gov but when transco came out they found the main incoming to be blocked.

 

[ShaunCorbs]

Neither. Have no idea why I typed that. It was a blockage in the mains. I thought it was a faulty gov but when transco came out they found the main incoming to be blocked.

becoming more common these days

 

[Harvest Fields]

becoming more common these days

First one I have had. At least they look like they are trying to upgrade them all.

 

[Last Plumber]

Is there a way to check flame rectification?

D44 in installer menu

 

[Hobo128]

Ok
Inlet working at meter 21mb. Inlet working at boiler 20mb. Probes are clean and have been cleaned again with wire wool by my self, I have removed them and are sparking. I've check resistance of gas valve which seems fine and have check earth from probe to boiler casing and boiler casing to pcb and so on. Condense is clear and all harness wires from visual inspection seem fine. I feel like it maybe pcb that is at fault. Any takers? Also , when boiler fires very very briefly burner pressure is -8mb

 

[Last Plumber]

Ok
Inlet working at meter 21mb. Inlet working at boiler 20mb. Probes are clean and have been cleaned again with wire wool by my self, I have removed them and are sparking. I've check resistance of gas valve which seems fine and have check earth from probe to boiler casing and boiler casing to pcb and so on. Condense is clear and all harness wires from visual inspection seem fine. I feel like it maybe pcb that is at fault. Any takers? Also , when boiler fires very very briefly burner pressure is -8mb

Where are you reading that -8 from?
Have you checked the polarity?