I just noticed this morning when I got to work that I didn't have any brake lights, after checking I didn't have turn signals either. But I do have just running tail lights. Is there a fuse that covers this? Or is it something else light the brake light switch? Any help is appreciated!
Oh yeah, it's on a 71 f100.

 

zoomer, There are only 3 wires going to the rear of the truck. One for the tail lights and the other two for turn & brake which are shared left & right.

First thing to do is check the bulbs, 1157s I think. There should be two filaments in them and each un-broken. My O, having a circuit tester like the one here is a must have Ford Truck Enthusiasts Forums - jowilker's Album: General photos - Picture It will allow you to test to see if there is any fire getting to the bulb. Start at the bulb then forward towards the front to find your issue. If the bulb is good, but no current in the socket you could next check the fuses near the hand brake lever. The switch will need to be on to test the turn signal function.



John

 

Also you might double check the tail light wiring connector under the rear bumper on the drivers side. Sometimes they get loose and crude builds up.

Tim

 

Ok guys thanks for the help!

 

This happened to me once, long time ago, but I vaguely remember..............
After checking from rear to front as John said, I ended up at the turn signal switch inside the steering column.

There was a brass rivet that had worked loose (hard to tell without the tester) and lost connection in the turn signal switch. I just pressed (hammered) it tight again, put the switch back in and all worked good. It is still in my truck working, but now I need to replace it as the plastic part that turns the turn signal off has broken inside and I have to manually turn off the turn signals.

Brake light switch is on the brake pedal arm, but I don't think that would stop the turn signals from working. Brake light power is routed through the turn signal switch though.

Hope you find something easy (and cheap) before you get to this.

 

I've checked all the bulbs, they are good. When I turn on the 4way flashers they work in the front. I took the wire off of the brake switch on the pedal and it ohmed out fine plus the wires feeding the plug had 12v. It's strange because I still have running lights in the back. Just not brake or turns.
I'm going to change the the flasher relay and see if that is the problem but I'm thinking it my be something with the wiring.
Maybe corrosion where my trailer pigtail is tied in.

 

try the ground wire that is attached to the body of the cab.

 

Go back and re-read post 2.

Tail lights are on a different circuit than brake/turn. Brake & turn share the same wires, one left, one right add tail for 3 wires.

Yes go to trailer connection next, a very suspect area. then check the connection at the end of the drivers side chassis rail. You start at the bulb and move to the front. Flasher shouldn't hinder brake light.



John

 

I did check the sockets and the trailer connection with a curcuit tester. No power at the rear. I'm gonna start checking wiring for issues.

 

Inspect the wires from the back to the front looking for chaffing.

It can also be in the steering column area, but you start at the bulbs and work forward.



John

 

Sounds like the turn signal switch to me, too.

 

I just replaced the turn signal switch a few weeks ago. LOL typical.
I did unplug the wires under the hood and checked for power going to the tail lights.
There was nothing going back there. I wedged the brake pedal down and turned on the left turn and it flashed .. the right did nothing. Seems wierd but it is looking like the turn signal switch in the steering column is the culprit. Or something in that area.

 

did you fix the problem and if so what was the issue

 

That thread is 16 years old but 99% of the time if you lose brake lights and turn signals at the same time it is a bad TS switch because all those lights are routed thru the TS switch.