My tail lights dont work or backup lights. I have changed bulbs and still nothing, the side markers work when the headlights are on. I have looking for a wiring diagram to go off of. The Haynes Manuel is not doing much help. Does anyone have a better diagram of the tail lights or even some place that I can purchase a complete wire kit for just the back end of the truck. I dont want to purchase a complete kit. Any help would be great. Thanks

 

Check you ground wire inside the taillight mount on the box, there is a ground for the side lights and one for the tailight . Since you have side light power is getting through, so I think the ground is bad or broken, once you remiove the tailght you'll see the ground wires screwed into the sheet metal.

 

They are hooked up but I will take them apart and clean them and make sure nothing is broken. There has been a trailer hitch on the truck at one point. I can see lots of splicing and cob work.

A good picture of a wire diagram for the back would be awesome.

 

I'm in the same boat. A good diagram of colors and locations would be greak, mmmkay...

 

Go to: www.autozone.com

Register (its free). You can then access alot of do-it yourself info, including complete wiring diagrams for these trucks.

 

I'm on my second f150 with taillight issues. My newest one had splice ***** of wiring for a trailer, plus a nice removable plug in connector. Go figure. Anyway, removing all of the junk splices and making sure all of the connectors are in good shape will be a good start. Don't even worry about the trailer lights for now, just strip everything to the factory wiring as best you can tell. then remove the taillights and then remove the sockets and bulbs and clean the contacts as best as you can. Then put the bulbs back in and begin testing the lights. Leave the bulbs out of the housing so you can wiggle them around and manipulate wires to find bad connections. Definitely check all of your grounds, and inspect the wires for rubbing, breaks and loose connections. Oh and if your handy with a meter, that helps too, but simple visual checks are always a good start.

Josh

 

I cleaned grounds, took off old splices and still nothing. Then I decided to take a 3,4,5 look at the fuse panel. I pulled the one out for emergency/tail lights. I found that the fuse was not blown but was only 14amp fuse. It calls for a 20amp, I used a piece of foil to bypass the fuse. IT WORKED, I went to the parts store picked up some fuses and changed them out. All I can figure is that the lower amp fuse was not letting enough juice thru. I never would of thought of that but wierder things have happened.

My only thing left is the backup lights.... is this part of the neutral safety switch?

 

Do you have a picture of your fuse block by chance? I'm having the same problem, but I can't read what is what. The lettering is so far gone I can't make heads of it. My truck is a 1979 F-150 Supercab.

 

Ya, the reverse lights is part of the NSS. I myself just got done with this ordeal.

 

This is true with automatic transmissions. If you have a manual transmission however, there is a plunger switch located near shifter linkages (depends on which of 4 manual transmissions you have)

Any problem with lights I've had on 1 bumpside and 2 dentsides (and I've had them), have been solved by checking and sometimes replacing the bulb sockets. Any wiring issues I've had have been within 2" of the bulb. I have a test light that is a sharp probe to stab into insulation, that has a bulb and a ground wire. One bad bulb socket can cause seemingly strange symptoms with the lights and the dash indicators. I've always found replacement bulb sockets for little money at local auto parts stores. Check that you have power near the bulb socket, and that grounds are good.

 

^ Yes but the OP has in his sig that it is an auto. Thats why I said it.

 

The fuse could have been blown without looking blown.

Next time you have problems with the taillamps, make sure you post the numeric sequence number of the vin. EX: T00001

The 1974 could have two different taillamp assymblies.

Before T00001, the taillamp lens and metal lamp housing are seperate pieces held together with screws. These will have 4 screws going through the lens.

T00001, and after, the taillamp lens and housing are one unit made of plastic. These will have only two screws going through the lens.

Yes it's a good possibility. It's located on the steering column. It could also be fuse or wire related.

 

I've had backup lights not lighting, be as simple as the bulb being loose or corroded in it's socket. I start by verifying power into the bulb socket with my test light probe. As far as the NSS: Two of the leads un-interrupt the ignition power when in the Park or Neutral position. The other Two power... and wire leading to the backup lights that is connected to power when shifter is in Reverse. Ive had three different transmissions including two manuals and an automatic in my 76, so I've spliced my own wire to the various switches I've needed, so I can't really check the color. I think the wire into the going into the backup light socket should match one of the NSS wires. Pull apart the NSS connector and jump the 12V terminal to the backup light wire terminal. I'd put my money on the problem being the bulb socket.

 

If it is the bulb socket, then we need to know if the 1974 truck was built before or after serial number T00001.

as I said before, 1973 and 1974 before T00001, have a metal lamp housing and taillamp assymbly. The sockets are not replaceable and the whole housing needs to be replaced, if that's the problem.

1974 after T00001, and 1975-1979 have a plastic housing, and the sockets are replaceable seperately.

 

I am trying to wire in a trailer light hookup, My backup lights haven't worked in the 2 years that I have owned my 1977 f150 but I don't care if they work. (I will fix them if I decide to restore it).