Dash Wiring problems of the 2005 Chevrolet Silverado 2500

I own a 2005 chevy 2500 silverado ext. Cab 4x4 since new. Last year in late March the wiring plug and resistor for the heater/ac blower motor shorted out, caught fire and melted right at the resistor. This is located on the passenger side of the pickup, under the dash, visible from below. The same thing, only not as severe this time, (I caught it early) just happened again. This time I took the pickup to the dealer to have them look at it and fix it. They replaced the resistor and semi-melted plug, the same fix I did myself the first time. They had no explanation for why this happened. With minimal searching on the internet, I found numerous occasions of the same thing happening to other chevy pickup owners. When these resistors fail, there is great potential for fire, personal injury. I burned my fingers pretty bad the first time.