Parent's Ferroli Modena 102 - erratic CH operation / turn-on

[Billy Bob Bob]

With a dodgy thermistor the boiler will light for a few seconds then shut off. It won't show any faults.

Sounds more like the pot is knackered especially if it has been used to turn the heating on and off for the past however many years. It is not designed for that.
If you are into electronics you could probably source one and fit it to the board.

I hope your folks have some other kind of heating as it is still 4 weeks (gawd is that all) to christmas!

good call tamz could be the pot never seen one fail though,mind it is a ferrolli though TBF the boards Honeywell seen loads of the resets break

 

[tamz]

If it has been turned up and down a few times a day for 9 years it is bound to be worn.

 

[Billy Bob Bob]

If it has been turned up and down a few times a day for 9 years it is bound to be worn.

yes it could,good call

 

[lauraeva]

Thanks for the replies.

Unfortunately I'm over 200 miles away from my folks so can't really do anything myself. I agree that the pot is highly likely to be shot, but sourcing one to fit the PCB and the knob spindle could be a nightmare !

The thermistors come in pairs at £26 inc VAT, PCB £203 inc VAT (Plumbase cheapest local supplier), so even speculative swapping of thermistor would be a fair bit of wasted cash if it didn't solve the problem.

If I were there I'd unplug the thermistor connector and jam a 10 or 15k resistor into the contacts to see if that would fire things up (obviously there would be no burner modulation and would have to switch off before overheat / limit thermostat cut out !). Would a boiler engineer do that sort of thing for diagnostics ?

Seems like my folks have found a heating engineer, colleague of an electrician they know, so hopefully he will solve the problem without ripping them off or fitting unnecessary parts ...