Observation:

Please choose how you wish to continue investigating possible overheat problems with this appliance:
USE DIAGNOSIS VIA DIFFERENTIAL CHECKS:
If the boiler can operate for at least 2 minutes this is the preferred method as it will require less dismantling of appliance.
USE DIAGNOSIS VIA INSPECTIONS:
If appliance will not operate for 2 minutes then it will be necessary to inspect possible faulty components directly.
Also choose this option if diagnosis via differential checks does not find any problems.