I had a similar problem without the clicking - I repositioned the thermal cut out switch on the CH flow slightly lower on the pipe to below the pressure switch (the black box with 3 wires coming out). I also reduced the contact area with pipe, and thermal paste on the cut out switch so it's less sensitive. This gave the controls a bit more time to switch off the flames before overheating.
If you can reduce the CH temperature, I think that would be better. But the accessable CH potentiometer reduces burner pressure and not set temperature, so you'll have to work out how to do this.
Dan Rhys
February 2010
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