vaillant problems?

I'm assuming Turbomax + (as the original turbomax only has one ntc).
The bottom ntc (above the aqua sensor), is only used for warmstart and would have no function in monitoring water temperature with HW in use

When running the water, does the yellow (burner) light go out at or around 84c and relight at or around 75c and cycle doing this? This would indicate a blocked Domestic heat exchanger.

Ideally the system temperature should reach about 83/84c and modulate around this temperature.

Carefree
July 2010