Truma boiler controls (5 Viewers)

[Figaro]

If I switch on my Truma boiler for 40c hot water it frequently doesn't fire up.
But I've found if I switch it to 60c for a few minutes first it works faultlessly even if I turn it back to 40c.
I'm guessing it's a poor connection in the switch or gummed up contacts ?
Blown air functions work as they should

Does anyone know if the switch can be dismanteled and cleaned up please ?

This is the switch

TIA

 

[dunnah01]

You can see the finger contacts behind the dial when you remove the switch A clean with a cotton stick and some acetone or contact cleaner may help

 

[Landy Andy]

I think on the 40 setting the temperature has to drop very low before the boiler will fire.