Replacement Battery for RII T3V, T3-V, T3-V+ Part NO 30-210218-17, ATB-1700

I would like to install a dual battery voltage  recently I have purchased a 12 volts battery coach  because Westfalia has two batteries auxiliary   and the main battery so I want to connect it and  have it like a constant voltage reading let's  install it as I already have the hole  drilled by a previous owner I'm going   to use the same hole and I'm going to  make it a little bit wider let's do that if your first position doesn't turn on the  positive your ignition switch is broken black and yellow wires doesn't give me a positive I want to  inspect the ignition switch what's wrong with that okay if your position one is not working  most likely you this circle is worn out   and you're not getting contact when it's  in the first position like it's supposed to   contact here and here let's try and bend it   a little bit this switch is for I reckon better  would be to change it I