Baxi 80e Combi: New PCB fitted, now nothing

[daKlone]

Hi All,

My Baxi 80e Combi started playing up today; no DHW or CH, flue/fan warning light flashing, fan not running but slightest whiff of volts at start-up.

So I replaced the PCB with a new one (the updated version), but now have nothing other than a green power light.

Tried holding the reset for upto a minute, tried turning off for a minute then re-powering with call for CH active - still nothing.

Any other suggestions on what to check?

TIA,
dK

 

[twgas]

Did you check anything before you decided the pcb was the cause of the original problem?

 

[daKlone]

Thanks for your quick reply.

Yep, checked:

Power to fan motor (none, other than the briefest hint my meter could detect at start-up);
Fan itself (applied power directly, works fine);
APS (n/c and n/o contacts are good);
DHW flow switch (working);
Overheat sensor (short...thinking about this again, can anyone confirm that this correct - short when cold?).

I've just re-fitted my old PCB and the old fault has returned the same.

 

[gas112]

You sure you have correct board and not the one for an 80e instant or an 80 eco ?

On fitting a new baxi board the left hand 2 red lights will flash this is then cleared by holding to reset

 

[daKlone]

I've no reason to suspect that it isn't the right part - 5112380 logic board. Came in the proper Interparts box and looks just like all the others shown on t'internet.

 

[daKlone]

Arrggh!

Just had it working...The two lamps you mentioned started flashing, so I reset it and tried DHW - success!

So I bolted the cover on the back of the control panel, closed it up and tried again...failure!

Can't get the two lamps to flash again now...is there some way to provoke them? So close, yet so far...

 

[Agile]

A comparative visual assessment between the two PCBs is the best way to see if they look the same. But when one has been upgraded that does not work.

It sounds to e as if the PCB was not the cause of your problem.

However, you have opened the gas sealed combustion chamber which we don't advise DIYers to do!

So my advice now would be to call a competent gas registered engineer who can check the safety aspects of your boiler.

On some of those Baxi models there are adjustments on the PCB which need to be made when a new one is fitted.

Tony

 

[daKlone]

Hi Tony,

What makes you say that it wasn't the PCB, given that a) the fault has gone (or at least changed significantly) after the swap, and I can go back to the original fault by re-fitting the PCB, and b) I just had it working, albeit momentarily?

Understand your comments re:safety and will do.

Thanks,
dK

 

[Agile]

The difficulty arises that when a PCB design has been changed they can respond differently to other boiler faults.

Now you might have had a fault in the original PCB as well as another external fault after you fitted the new PCB.

Or perhaps just the external fault!

Can you look closely at the connector pins in the plugs to the PCB? Sometimes they move upwards and don't make a good contact.

Its not helpful that on that model the wires to the PCB do not sit loosely and are stressed when the cover is fitted. Not my idea of a good design!

Tony

 

[daKlone]

That's true, layered faults are my favourite...not!

I've gone over the connectors and nothing "rides up" when fitted.

If I follow the fault-finders through in the manual, they all terminate in "replace PCB", which I've obviously done. Frustrating!

 

[Agile]

Have you looked closely at each individual connector pin?

Unless you are short sighted you would usually need a magnifying glass!

Tony

 

[daKlone]

I'll have another look tomorrow I think...I'm liable to break something after fiddling with it all day and getting next-to-nowhere

 

[gas112]

Part bought of the internet ? is it from a big company and thus brand new.
Or off an individual and thus possibly been used
These boards have come in a sealed bag then bag sealed to the interpart box for around 2 yearsnow before that they just came in a bag in the box

Board usually costs around £100 to £115 including

 

[daKlone]

Bought from a local individual, claimed as new. Came in a proper Interpart box wrapped in pink ESD bubble-wrap with a little note about resetting the boiler after installation.

No obvious signs of previous use, but then I suppose it would be difficult to spot on something like this.

I guess I could ask him if he has another I could try.

 

[Agile]

I doubt there is anything wrong with the new board.

Look at plugs and nearby bits!

Tony