Oil boiler problem (cuts out)

[News]

We have an oil fired boiler that started to cut out a couple of years ago, and was eventually fixed by replacing the control box (Honeywell TF832 3). The same thing started to happen a few weeks ago, so I bought a new control box, plugged it in and fixed it - temporarily. Sometimes it runs fine for days, then is a bugger to get going. Tonight, I removed the control box, sprayed contact cleaner (Servisol Aero Klene

50) all over the contacts within the boiler, replaced the control box, and it is running.

Coincidence, or could the problem be nothing more than dirty/corroded contacts that are temporarily cleaned whenever a control box is unplugged/plugged in?

[Dave Liquorice]

Have you cleaned the photocell?

[News]

I don't know where it is, or what to look for.

[Dave Liquorice]

Small silica glass window behind the jet(*) so it can be illuminated by the flame. Google for your burner and you may find the manual and/or exploded parts diagram.

(*) IIRC ours got sooted up just as I was about to go away for a few days, so it was a bit of a rush job and one I hadn't done before so memory isn't good. Dirty photocells are a common cause of oil boiler lockouts.