Gas boiler: intermittent fault

[3loader]

Hi A few days ago my Baxi 105e boiler failed to function.
The flashing neon indicated a fan or air pressure switch fault. Upon looking the fan was not operating but I isolated this and when tested functioned perfectly. This made me think maybe the the flue air pressure sensor.
I cleaned the contacts and and blew and sucked the tubes.

Following this the system worked again. 24 hrs later the problem recurred. Similar actions got it going again. Does this mean its definately the air pressure switch as the manual fault finding flow chart suggests the fan should still operate if that is the fault.

The other suspect could be the water pressure microswitch. Can I short out the contacts to test this theory if the fault reccurs.

The pressure guage on the front panel (when at rest is reading just above 0.5 bar.

Thanks in advance.......Kev

 

[gas4you]

The fan should spin first, then the aps detects the fan is spinning correctly.

Some boilers pcb's check that the aps is in the correct position first before allowing the fan to start, can't remember if yours is one that does this though

Following fault finding chart to the letter.