Promax noise

[BLOD]

Went to look at a Promax 15/2 heat only today that makes quite a loud low pitched vibrating noise on start up.
It makes the noise nearly every time the boiler tries to fire up and usually takes 4 or five attempts to light.
Ocassionaly it won't make the noise and lights first go.

I'm thinking the fan is on it's way out or maybe pcb isn't putting out the correct fan voltage
Has anyone come across this before ?

 

[JamesyGoosey1]

They have redesigned the spark electrode and rectification probe cause of problems with arkin on the case instead of sparking in the combustion chamber pal. Just check that when the ignition process is in full swing

 

[GrahamM]

This is a terrible boiler.
The noise may be attributed to a rough manufactured venturi funnel that requires the burrs being smoothed off to prevent howling noise.
There is also a modified electrode as mentioned above that prevents the electrode arcing out on case.