Sometimes when I shut off my 2000 F150 XL I hear a relay clicking sound from behind the instrument cluster. Another problem is the heater blower continues to run when it is set in defrost, the fan is in on or off position and the truck is shut off and the key is removed. They are separate conditions, haven't noticed them occuring at the same time, but either one of them will cause a dead battery. Having the heater control set to defrost is something I can shut off every time I quit using the truck for the day. The clicking sounds I can't control, it doesn't happen every time I drive it. It may just click 2 or 3 times or it may continue for many seconds. Any ideas? I don't have access to a code reader.