I have a 2002 SCrew Xlt with 5.4 and having troubles with getting the blower to work. In all positions on functions switch fan will not operate, if i jumper out the blower relay, fan works on all speeds and functions. So here lies the true problem i am having, have power at #1 on function switch plug and no power at the relay to energize it coming from #4 of the function switch. Wire has checked good in continuity. In other words take the function switch out of the system and it works fine. Have tried 2 other function switches and still no joy, is it possible that a vacuum leak could cause the switch to be inoperable?

 

may sound like a stupid question but you check the fuse?

 

Fuses are good, not getting power through the switch to the relay.