Worcester 35CDi Lock out fault. Flame sensor & board cha

[marsh2000]

I have a Worcester 35CDi II gas boiler that is going into lockout when it starts up (CH light flashes slowly). When the hot tap is turned on, the DHW light comes on, it starts to spark in the chamber and the gas then lights. The sparking continues for a few seconds and then the boiler goes into lockout. The same thing happens when the heating tries to start up.
I have changed the flame sensor and the control board but this has made no difference.
Has anyone any suggestions or ideas what the problem is?

 

[Dan Robinson]

Get someone in who knows what they are doing.

I Suspect you have wasted far more money than it would have cost you to have done it properly in the first place.

 

[marsh2000]

I did get an engineer in who changed the flame sensor and then rang Worcester technical helpline who suggested it was the control board. I changed the control board this morning but with no joy. I was hoping someone might have a suggestion so that I could have some HW before the engineer comes out on Monday morning.

 

[Dan Robinson]

I have a fair idea what it might be, but it involves poking around in the combustion chamber so not advice you'll get from here.

 

[bazdaman]

+1 and whats wrong with a kettle till monday,

 

[petit_pablo]

Good old worcester technical. Funny how its always the board

 

[marsh2000]

Just an update for anyone with a similar problem. I found a page on GasBoilerForums.com suggesting moisture in 21 way low voltage connector on PCB. Having already inspected the connector under a magnifying glass I didn't think this would be the problem but I was willing to try anything.
I got the hairdryer out and gave the connector a good blow dry.
Success!
So £10 on a sensor, £65 on a PCB and £70 on an engineer all down the pan and 2 minutes with a hairdryer fixed the problem.

 

[Boilerman2]

Congratulations on treating the Symptoms!, NOW you need to find out the cause - where is all that moisture is coming from?, cos believe me that is NOT NORMAL!!

 

[Dan Robinson]

Glad it's working for you. ? Can't beat a bit of luck over judgement

 

[Porque223]

Just an update for anyone with a similar problem. I found a page on GasBoilerForums.com suggesting moisture in 21 way low voltage connector on PCB. Having already inspected the connector under a magnifying glass I didn't think this would be the problem but I was willing to try anything.
I got the hairdryer out and gave the connector a good blow dry.
Success!
So £10 on a sensor, £65 on a PCB and £70 on an engineer all down the pan and 2 minutes with a hairdryer fixed the problem.

I had one of these, moisture caused corrosion on the PC board edge connector.
24vac in one side and 3 vac out the other side into a 10 megohm input resistance DVM and the connection resistance then comes out to be
3v/10M = I = 300 nA
(24-3)/I = 70M

I at first didn't believe it.

 

[Agile]

How can a new Worcester PCB only cost £65 ?

Tony