Let there be two lights
QThe bedroom of our boat has two 12v spotlights connected to a two-gang switch. Both lights are wired to one switch and I would like to have them working independently, however, a new switch would be needed. Will a ‘normal’ 240v switch from my local DIY shop work with a 12v system?
Mains (230v AC) switches usually give no problems on 12v DC lighting circuits, but no one can guarantee that will be so in every case. When any switch is opened, a spark tries to jump between the two opening contacts. On a DC circuit, the spark will keep going until the gap is too large for 12 volts to push a spark through ionised air. On AC mains, the current turns itself off every 100th of a second so the spark stops quickly. This means the contacts on AC switches are usually smaller than on DC switches and DC switches could use additional means to deal with the spark. This is not normally an issue with resistive loads such as filament light bulbs, but it is a problem with inductive loads such as motors and other items with coils in them. There might be a longer-term problem with 12-volt LED bulbs that have built-in electronics. So, usually, a mains switch will work for DC lights but there is always a chance that it could fail before a DC switch.