Baxi combination boiler problem

[D.M. Procida]

I have changed the seal and diaphram on the three-way valve mechanism (that detects when water is being drawn from a hot tap) on our Baxi 105 boiler.

After replacing the parts, it won't start up.

The green power light is on. When the hot tap is turned on, the piston pushes the miroswitch that fires up the boiler, but the gas doesn't turn on.

If I turn up the central heating thermostat, the boiler makes the noises it would make normally, of things powering up to heat and pump water, but then goes off off again after a second. It repeats this in a regular cycle, ever two seconds or so.

Any ideas what's going wrong?

Thanks,

Daniele

[cpvh]

Is it fan flued?

If so, it would need th sense either that the fan was running, or that it was doing it's job before it lets gas out of the burner. Might you have missed a connector somewhere?

[A.Lee]

If it was working beforehand, then it is 99% certain that it is something you have done. Electrical plug-in connections would be my first point of call, then any other connectors you may have displaced/put on wrongly. Pressured up correctly? Does water come out of the tap? Is the heating working? Does it try to light up? Water on a circuit board? Water in any other connections that may affect use?

[geoff]

In message , D.M. Procida writes

If you've not disturbed anything else, the first obvious thing to look at is the connections to the div valve microswitches

You have given a very woolly description of what is happening

"he boiler makes the noises >it would make normally, of things powering up to heat and pump water,but then goes off off again after a second"

is the fan coming on?

does it actually light the gas?

[D.M. Procida]

Thanks for the various replies.

I found Baxi's troubleshooting flow-chart, which took me to "replace the PCB".

I took a closer look at the board, and found a drop of water on it. After a few minutes' work with a hair-drier, to my relief I was able to get it to start again.

So I think that there must have been some damp on the board.

Daniele

[geoff]

So, where did it come from?

Did you get it on the pcb when you recon'd it or do you now have a leak?

If the "water" is from the CH system side, wash the water off (e.g use a bit of IPA) don't just dry it, as it should have inhibitor in ... which is corrosive and will track again when damp or corrode component legs away

[D.M. Procida]

There was a little spurt from the hot-water valve mechanism, where I replaced the seal and diaphragm.

Daniele