Occasionally, and it's getting worse, I'm getting an electric hum from the passenger side of my truck. When it starts, and I do something electrical such as roll up my window, the pitch increases, it also increases with acceleration. I'm thinking its the heater/AC blower motor or the control module. Any other suggestions? If it is the blower motor, how hard is it to change? I don't want to take apart the entire dash, but if I can get to it through the glove box I'll do it. Has anyone had this happen?