Not sure what the deal is with these factory rocker switches, there seems to be alot of power going through them, not sure if they used a relay or not, i'm guessing not, as my original one wore out and the plug on the back had melted through the years.
Not in a short amount of time or anything, but is definately due for replacement.
I found a nicer switch and plug setup out of a junkyard truck, still haven't replaced it yet though. back when it quit working, i did something similar to what you have there and wired in a toggle, 3-way switch (low-off-high) setting switch, works fine, but just not factory :P
A previous owner even routed heater hoses all the way back, and up to the ac area, with this smaller, long looking heater core type thing, so i have rear heat, without the floor mounted unit, really nice, does an awesome job too.
