Thorn 25/30 ah fan problem

[Kris plumb]

I have been asked this one by a customer and am not sure as it’s a old boiler I no nothing about how it’s meant to run.

So the time clock packed up so I replaced it and all was well but now the customer is telling me that the fan runs all the time, even when the stat has cut the burner.

Is that normal or could the fan limit control have packed up to, like I said I am unsure as to the function befor I replaced the time clock.

 

[Last Plumber]

I think this should be in gas safe only section. There will be answers there I am sure.
Ask @ShaunCorbs if he can move it?

 

[Kris sparky]

This boiler has a high/ low stat that turns the fan and gas on and off. The high limit is 112c ( over heat this shuts the gas valve this should not operate in normal use) the low limit stat 30c this turns the fan on when the heat exchanger is over 30c and off below 30 c, this boiler is very simple electrically the time clock you replaced only opens and closes the 24v stat/gas valve circuit. The hi/ low fan stat is an obsolete part in the uk but a universal replacement is still available from the stat manufacturer in the USA