Check this out. When I turn on the headlights on my 1979 F150 4x4 everything is fine. All markers, head and tail lights work. But when I hit the breaks the drivers side break light goes completely out. The passenger side works fine. Wait, there’s more. When I depress the breaks the tail lights will come back on but if I use the left turn signal it goes completely out again but this time it stays off. I have to turn the right turn on and only then does it come back on. And ounce again if I hit the breaks the left side goes dead and when I release the breaks it comes back on. I just bought the truck and it started doing this once in a wile. I know because I got a fat ticket for faulty equipment but when I went to check it out it worked fine. Now it does it all of the time. Any ideas?

 

Bad grounds/connections or bad bulbs. I have to fix these problems on a weekly basis with my highboy till I get all the bugs worked out.

 

I would start by checking all your grounds, your definately going to need a schematic and a test light. While your at it, look over all your other connections and make sure there not rusted or corroded.

 

Check the bulb socket on the side that is giving you trouble. There is piece of steel that goes through the side of the socket and touches the side of the bulb. I am willing to bet that the steel has rusted off like happened to both of mine. When that happens, your bulb loses its ground and starts looking for a ground elsewhere. This is what causes your funky problems.

To fix it, make a new piece of steel or copper the same width as the original. Solder a piece of wire to one end. Then, push the steel through the slot in the side of the socket where the original piece was. After it protrudes into the socket about 3/16 inch, bend it over so that it goes down toward the bottom of the socket. Put the bulb back in. The new steel will now touch the side of the bulb base. Lastly, attach the piece of wire, that you soldered to the end of the steel, to a good ground back by the taillight assembly. This should correct the problem.

 

The sockets are available new too.

 

Also make sure that someone did not put a single contact bulb in one of the sockets. I have seen that before and it did some wierd things.

Good luck,
Doc

 

Everything you have mentioned runs thru the turn signal switch.

Have you checked the tech articles for a Trouble shooting guide ?

 

I too recomend the checking the sockets. I had almost the exact same problem on my '77 F150, except mine went funky when the headlights were on. I redid all of my grounds and replaced all of the bulbs and still no dice. Then a friend of mine told to check the sockets, which I assumed to be fine. Anyway, I ended up replacing all of my sockets. Three of them had the metal inside corroded causing the funky problems. Hope this helps.

 

Make sure you have the right bulbs for the sockets, and that the bulbs are installed correctly in the sockets. Make sure that the grounds are good, een the big ones like motor to frame etc.

 

just got done with this one. bought a new socket for $5.83 special ordered at autozone. came in 1 week later. already had wires connected and ready to crimp. works fine now. with mine, the tail light worked if I didnt have the lights on. with the lights on, I would put on breaks but the light went out. changed bulbs, tested with meter, and said enough. fixed the problem. you can get it faster if you pay more, or they have it in stock.

 

You guys are so awesome, thanks for your help. I fixed the problem and learned a very good lesion. I changed the bulb like was suggested and I noticed something strange. The bulb that was in the funky socket was not nearly as bright as the other side. Also when I took it out I noticed that the bayonet base was brass instead of that nickel or chrome material that was on the other bulb. The brass one was the same value so I didn’t think anything of it. I put a new one with the nickel bayonet base and bent out the ground tang slightly and “BING!” Problem solved and all I had to do was replace the cheap piece of junk bulb. You guy’s rock! If only my faulty equipment ticket was that cheep. Thanks