In my conversion I am hoping to do all led 12/24v dc lighting. I would like to know what type of switches to use especially if you want to do a 3 way location. Ac switches are not apprved for dc so what does everyone use. The marine switches made by Carling switch are great but very expensive. So what is the suggestion ? Thank you.
I bought my DC switches on eBay, where lots of surplus stuff ends up. I paid maybe ten bucks for 50 switches, and they were SPDT, which means they can be used either as On/Off or three-way. I paid dearly later, though, when I had to have the switch plates custom made. I wanted stainless plates; it would have been much cheaper in plastic.
You can buy single- and multiple-gang DC switches with plates at many surplus stores such as Northwest RV Surplus in Eugene.
All that said, for very low-current (a few amps for lights), 12-volt applications, many household AC switches will work fine. They will not be stamped on the package, but if you call the manufacturer, they can often tell you the DC rating of their standard AC switches. You want the positive snap-action style with no illumination or other features.
The reason why DC ratings are much lower than AC ratings (and why some models can not be used with DC at all) is arcing. AC voltage passes through zero 120 times per second, so any arc that forms while the switch contacts are opening is extinguished in a maximum of 8.34 milliseconds. DC voltage is constant, and so any arc that forms will not be extinguished until the contacts move far enough apart to do so. Arcing can pit and erode the contacts, and/or cover them in carbon deposits, all of which increases the resistance of the switch. This ultimately leads to ohmic heating, which can be hazardous.
Opening a 12-volt circuit carrying just a few amps poses very little risk of arcing, and most standard, snap-action AC house switches will work fine. Again, contact the manufacturer and ask what the DC rating of the switch would be.
If you want illuminated switches or other special features, you will need to stick with purpose-built DC switches rated for the voltage you are using.