A gentleman at my workplace, who has a 1999 F150 asked me about his truck and if I can offer any help. The blower motor cuts in and out and temporarily fixes itself when the door is slammed. I do not know much about the electrical systems, but could this be a bad relay or just a shorted wire?

Any help would be appreciated,

Thanks,

Tim

 

It might be the relay, but probably not. Check the resistor connector for signs of heat. It's in the R side of the blower housing above the passenger footwell.