Might sound like a weird question. I have a 2004 F150 Lariat with auto climate control. Everything is working but the rear window defrost. The button will illuminate for a split second and I can hear something clicking in the fuse panel under the passenger side dash area. Is this controlled by a relay or fuse? I looked at my fuse diagram but saw nothing referring to rear defrost. Anyone have a clue where the fuse or relay is located and what the clicking sound is?

 

There's a 40 amp fuse (F114) then Relay 04 should be the relay controlling it (which is likely the click you're hearing). Check F114 and see if it's blown.

 

Thanks! I'll check it when I get back from work.