Help to check PCB - please!

[zappastix]

Hi

I have a problem with my Alpha CB 28 boiler.

The fault finding section points to the "Air Pressure Switch".

I have replaced the Air Pressure Switch, but the same problem remains, which is the 2 front panel lights are flashing together.

I have checked the flue - that's clear, and blown through the plastic pipes.

Funds are very tight - so I trying to determine if the PCB is at fault.

As it would be cheaper in the long run to replace the boiler, than a new PCB.

(the air switch was £46 - I dread to think what a PCB would run to).

MY QUESTION

The fault finding section also says to check out the PCB.

It says;

PCB - M5 connector, is 24 V DC
across terminals 15 and M6 connector terminal 20

All I would like to know is this (testing the PCB);

As the boiler tries to fire up just before the air switch is supposed to start,
do you put the 'probes' of the volt meter on terminals 15 and terminals 20 TOGETHER?

Any help or suggestions would really be appreciated, as it's getting very cold where we are now.

 

[Paul Barker]

In my experience as an Alpha service engineer, this pcb is bullet proof. The aps is also very reliable, I would suspect the fan, it might be enough to clean the hamsters wheel, blow out the sense tube between the fan housing and the aps, and lubricate the fan baring this time. Eventually you might need a new fan.

I would most certainly not replace the boiler.