1974 F100.All lights,signal lights,brake lights,4 ways are working except on drivers side rear where i have no 4 way flashing,or brake light,but have signal and running light.Replaced fuse,bulb,and cleaned ground's at rear drivers side bulb housing.Noticed at affected bulb receptacle that hot ( brown ) is a little loose in socket,but can't remove to have a look,but feels somewhat solid in the socket.Also wiring at other side,and under truck to other side looks ok.Should i just replace socket,or is there something i'm missing further up the truck,or in the dash that these rigs are famous for causing this.This is my 2nd FE,and my other '74 does'nt have any trouble like this,neither do either of my '77's.Any help greatly appricated.

 

If I interpret your post correctly, you're saying that everything functions normally on all four corners, with the exception of the rear driver side: on that corner, you have running lights and turn signal, but no 4-way or brakes. Did I get that right?

The BROWN wire is for the running lights, and although you said it looks a little loose, it's working, so let's take that out of the picture for now.

The brake, turn, and 4-way are all the same wire going to that corner of the truck. If at least one of them works, then that proves out the wiring to that corner, the socket, and the bulb. That means the problem has to be upstream, but you're saying the other items work at the other corners, which would point to the bulb or socket. In other words, the symptoms you've listed contradict one another.

The only explanation I can think of is that I read your problem incorrectly. Or there is some goofy ground issue that's not obvious to me. Does the problem go away or come back based on the running lights being on or off?

If you see any wiring loose in the socket, I'd replace the socket anyway - other problems aside.

 

Thankyou for writing.Yes,you did understand the problem as explained in my post.The condition exists when running lights are on or off also.The other colour wire is black with yellow,and i assume this is then the wire for brake,turn,and 4 way (as on my other FE,it's a different colour,but routs the same way)...but turn works,run works,brake and 4 way don't.I should of mentioned i pulled a trailer brake set up out of this truck that was a horrible instal from p/o.As far as i could determine,they just wired into the ign. switch,and an existing factory hot when pulling this mess out.The fuse was blown in the 4 way/brake light circuit which i replaced.I'm not sure if they screwed anything else up under the dash,but like you said,all lights in front corners,and even factory cab marker lights on roof,and front side body marker lights are working perfectly,as is the rest of the entire electrical circuit,and the new fuse is holding so far today,so i would assume from the shoddy install of trailer brakes,they must of blown the fuse,and not known.I've just bought this truck,and like my other FE, love it.It's orange,with factory fade striping on bottom,it runs like new,and has only 85,000 original miles.Just another great surviving ford FE that gets spoilt pretty good now i own it.I'll swap out the receptacle,and see what happens,if that does'nt fix it...not sure what i'm going to do....
Thanks for writing,and your help.

Blue Mule