Need some help. I just changed the lower ball joints on both sides don't know if that matters. I now notice the 4wd won't engage. When I turn the switch on dash to put in 4wd hi. Nothing happens no lights no click nothing. It's like there is nothing there. When I start it up and runs it check the 4x4 light lights up. Any help would be great it worked perfectly last time I used it. Thinking a fuse or vacuum line.

 

You didn't specify a year, but for most fuse #104 under the hood controls the 4WD system.

 

BTW, if it were a disconnected vacuum line, the transfer case would still shift. So this sounds like an electrical issue.

 

Sorry it is a 97 expedition EB. Yeah there is nothing happening when I switch the switch... No lights or engaging

 

In that case check the 30-amp fuse #17 under the hood.

 

Will check when I get home thanks. Do these fuses just blow due to age or is there something else that would cause it

 

Usually something causes it to blow. But hey, nothing lasts forever so changing it is a good starting point.

 

My 4hi and 4low quit working a while back and it was fuse #16- 40a maxi under the hood. I still had A4wd though.

 

Fuse #16 has absolutely nothing to do with the 4WD system. Perhaps when you were in there tugging on fuses you got #17 to reestablish an otherwise bad connection.

 

Apparently it does. I have no idea why though. I asked about it a while ago. Fuse 16 was blown- had 2wd and a4wd only- replaced it and everything was right in the world again. If I remove the fuse I have no 4hi and 4 low.