Typically I install a pair of standard Bosch 40a relays in front of the radiator yoke on the drivers side... Open the headlight harness & identify the power wires from the bulkhead to the high & low beam headlights... These are now going to be the control leads for the relays connect them to terminal 86 of each relay.. Add ground wires to terminal 85 of each relay... run a couple 12 gauge wires from the main terminal to terminal 30 add a 20 amp fuse to this wire & finally hook the headlight feeds up to terminal 87 keeping the high & low beams tied to their original feed.... Basically the relays act as the switch carrying the whole load, the original switch & wiring only carries the approximate 300ma load required to trigger the relays.... Adding the same to your blower motor means the blower switch no longer carries the load which often burns out the switch and the blower motor spins quite a bit faster...