1998 Grand Marquis Blower speed
 

Hi, blower speed only works on HI. I was wondering if this could be a resistor type control that went on me in my 1999 F150? If so can you help with the location of the control that runs the blower speed. Also any advice on changing this part out. My pickup was very easy to swap out. Probably it is rusted out, like everything else on our vehicles here in Maine. Thanks for your help.