Predicting a fault.

[M77]

Hi all, just wondered if anyone could help. Had a call from potential customer today asking if I could replace a part on their boiler and how much I'd charge.
They proceeded to tell me that they had their boiler serviced last month and the engineer told them that the aps was on its way out.
I asked about the fault and they said that they haven't had any problems with the boiler prior to the service or since which confused me to be honest.
My question is how could the engineer predict the aps is going to fail without the fault happening? Is he pulling a fast one or am I missing something?
Thanks.

 

[tamz]

Maybe he is a psychic?

 

[galaxy_plumbing]

maybe he is smoking manuals, anyway go and replace APS

 

[diamondgas]

Intermittent fault .. testing resistance through aps microswitch can tell you a thing or two ... blowing down it and then it working thereafter tells you a thing or two.... Time it takes to recognise the fan before ignition tells you a thing or two.... All possible indicators to an aps failing at some point! Just guessing mind as I have no idea why anyone would suggest a possible issue but do nothing about it...!

 

[M77]

Thanks guys. I'm thinking the only possible indication would be slow ignition due to aps not recognising fan, otherwise I'm stumped as to how you'd know it was about to fail without seeing the fault while there.