What do you mean by "burned up again"? Is that your way of saying it doesn't work or did it really start on fire?
If it started on fire or was smoking, look where rain water drips when you open the door. I'm aware of at least one model that needed to have the mirror switch redesigned to prevent damage from water dripping from the front of rail along the left edge of the roof.
If the switch controls the right side mirror too and both mirrors are not working, check the wires between the driver's door hinges. A frayed or broken wire may let the system work when the door is opened to a certain point.
There isn't enough current going through the switch or for long enough to overheat the contacts or connector terminals so arcing shouldn't be causing the problem. Even if the original switch was defective, it's very unlikely a second one would fail too without some other underlying cause.