Be careful about running several accessory items through the ignition switch, as the contacts inside the switch can overload and burn. I like to install a small auxiliary fuse block somewhere out of sight, and power it with a continuous-duty relay like the square Bosch type that's used for electric cooling fans, driving lights, etc. A heavy wire back to the battery cable connection at the starter, of maybe one from the ammeter can provide power to the relay contacts. The only load on the ignition switch that way is a very small current draw to power the relay coil. The voltage gets switched on and off by the ignition switch, but the relay carries the load of the accessories. We wired cab and clearance lights on big rigs that way to take the load off the light switch.
Jerry
