Quick Question from a Spark

Baxi 105e / Fault - Fan or Flue fault lights. (An antique, I know).


My old boiler has developed an intermittent fault while delivering HW and CH.


So I've taken the front off and ....

There is 240V going to the fan and it appears to be rotating smoothly, when the burner is in operation.

There is only 170V going to the APS from the PCB:
L-N is 170V,
L-Control Wire (Black) is 170V,
N-Control-Wire is 0V

....all while the burner and fan are in operation.

The micro-switch on the APS is rated at 250V/1.5A.

Am I right in thinking the PCB is faulty, i.e. not giving the APS micro-switch what it needs?

I've got the plumber coming round tomorrow night to quote for a new boiler.

Time for a new boiler perhaps?

Many thanks for your advice.

"N-Control-Wire is 0V"

What's this? blown or blue?

Sorry that wasn't very clear.

Live L is brown.
Neutral N is blue.
The signal/control/switch wire from the micro-switch is black.

Testing live to neutral at the APS is 170V.

Testing live to signal/control at the APS is 170V.

Testing neutral to signal/control is O(zero)V.
All while the burner and fan are working. The flue looks clear and clean from the outside.



I'm expecting that there should be the 240V going to the APS from the PCB and this is why the APS is cutting the burner out? So PCB at fault? But then why would it start up?

I suppose I'm just in denial that it's time for a new boiler.

Thanks guys.

will be the PCB