biasi m90 24spulsing fan

[buckley plumb]

been to a biasi m90 24s to day no flashing lights but no hw or htg. the fan was pulsing on and off. checked aps which was ok .biasi are saying its the ignition board the relay on it is sticking.if i removed the silicon aps tube the fan constantly runs at a fast speed but if i removed the wires from the aps and linked the common and the normal closed the fan run super fast.was told by biasi if fan runs when aps silicon tube is pulled off then its the board relay.ordered board but whats puzziling me is why the fan runs super fast when the nc is linked to common and why removing the aps silicon tube makes fan run .

ant

 

[mountainman]

These things are getting far too complex, we'll all end up being parts fitters before long..

 

[diamondgas]

been to a biasi m90 24s to day no flashing lights but no hw or htg. the fan was pulsing on and off. checked aps which was ok .biasi are saying its the ignition board the relay on it is sticking.if i removed the silicon aps tube the fan constantly runs at a fast speed but if i removed the wires from the aps and linked the common and the normal closed the fan run super fast.was told by biasi if fan runs when aps silicon tube is pulled off then its the board relay.ordered board but whats puzziling me is why the fan runs super fast when the nc is linked to common and why removing the aps silicon tube makes fan run .

ant

Pulsing on and off deffo sounds like PCB as the aps switches but something in the pcb doesn't so back to the beginning we go!!!!

Removing the tube doesn't allow the aps to open and tell the pcb the fan is working so the fan runs constant.....

No idea what swapping the wires does as it'll confuse the pcb

 

[buckley plumb]

Pulsing on and off deffo sounds like PCB as the aps switches but something in the pcb doesn't so back to the beginning we go!!!!

Removing the tube doesn't allow the aps to open and tell the pcb the fan is working so the fan runs constant.....

No idea what swapping the wires does as it'll confuse the pcb

thanks replaced pcb and it works just wondered why the aps works differently than most boilers, most if you link the no and common the boiler will go to ign but not on a biasi.

ant