John,
The exact number varies with the construction of the switch, but a rule of
thumb is that the D C current rating is about 1/8 that for A C.
As the switch is closed or opened, there is an arc as the contacts separate.
Since A C reverses itself 120 times a second, the voltage passes through zero
120 times a second. That quenches the arc, and it won't melt any more metal
off the contacts.
With D C, the contact points are a miniature arc welder. As the points open,
an arc is established, and it keeps burning until the points are far enough
apart to cause it to quench.
I would suggest buying switches from an electronic supply house that will have
all of the voltage and current parameters available. If you can't find such a
source, then I suggest that you replace your ignition switch with one rated at
25 amps.
Jim Vance
va...@claflinwildcats.com
