I have two DM02 boards in my ComfortII system. They have worked fine for many years. Recently I have had some strange behaviour on one of the DM02 boards.
I wanted to see if there is a way to test that it is functioning properly or do I need to replace it.
When I press the SW2 switch on the board it is very slow to respond. Sometimes if fails to ring the telephone. Before replacing it, I just want to make sure that the board is in fact bad.