The tailight and separate turnsignal on the left rear are causing me some problem. Here is what happens:

-When the turn signal is turned on the turnsignal light flashes as it should. When the lights are turned on the taillight flashes and not the turnsignal light.

-The brake light comes on when when the brake is applied as it should. When the lights are on and I apply the brakes the taillight goes out on the left side.

-When the lights are on and the left turnsignal is on the tailight flashes as decribed above. When the brake is applied everything on the left goes out.

-When the four way flashers are turned on the turnsignal light flashes as it should. When I then turn on the lights the taillight flashes and not the turnsignal.

My truck had the turnsignals added after the factory probably at the dealer. They are the signal stat type, not the type in the collumn. When I rebuilt the truck 6 years ago I tried to use the taillight as the brake, turn and tail light but could not figure it out, so I added the turnsignals. Look at my gallery for the setup.

It sounds like I have some wires crossed. I looked at the wires slong the frame and have not found a place where both wires are bare and touching each other. Is it possible that one wire could be bare and touching the frame and the other could be bare somewhere else and touching the frame at an other spot? My right taillight and turnsignal and brake lights are working fine.

thanks!

abe '54 F-100

 

My 48 did something about as strange, only it was the right side that was screwed up. Simple fix to try first. Run down the wires to make sure they go where they should. All mine required was a ground wire from the bucket (that was causing the problem) to the frame rail. Now all is wonderful. Hope your's is as simple.

Bare wires can cause it too - do yourself a favor and buy a taillight harness. They're fairly cheap and will save untold aggravation. Or buy a spool and run your own. Mine once shorted where the wire got under a tailpipe hanger and pinched thru the insulation.

 

I'd have to actually see it but it sounds like the socket is wired backwards or the bulb has been forced in upside down. Take off the lenses and see which filament is lighting up on each side. Make sure the bulbs were put in correctly, the pins on the side of the bulb are at two different heights make sure they match the slots in the socket, and they are turned to the full lock position. A bad ground can cause wierd symptoms, Run a temp ground wire from the outside of the socket to a clean metal bolt on the body or chassis to see if that clears it up.

 

One other thing, is your truck still 6V + ground or has it been converted?

 

AX, it is the original 6 volt positive ground. I rewired the truck in 1999 after I got it back from the body shop. The lights worked fine until a couple of weeks ago. The bulb was in correctly. I put another bulb in, same thing.

You say a bad ground could cause goofy stuff like this? I will running another ground wire to see if solves it.

thanks, abe

 

A little additional information would be helpful in troubleshooting this.

1 -Was everything working fine and then it suddenly started doing this?
2 - Was this originally an intermittant problem that has become permanent?
3 - Did you make a repair/upgrade or modification to the truck immediately after which this occured?
4 - Has the truck been sitting for years, everything used to work and now this is occuring?
5 - Did you recently re-wire the truck, it used to work before the re-wire and now this is occuring?

There are a number of different possibilities. Where I checked first would depend upon what the answers are to the questions above.

Bad/corroded grounds cause all sort of bizarre things to occur. Ask anyone you know with a boat, expecially one that gets run in salt water. And boat trailers are just as bad.

If it had been working and suddenly started doing this, my bet would be the ground. It could be a wire chaffing problem but if that were occuring. I would expect that you would see bulbs burning out like crazy since they would essentially be your fuse. Another symptom of chaffing would be a burning electrical smell from a hot wire grounding out.

Tell us more.

 

Make sure there is a good ground connection between the body and chassis, but I'd bet it's in the light unit. I'd also start thinking about converting to 12V neg ground sometime in the near future, it's much more reliable and not hard to do.

 

A VOM and a large sewing needle makes troubleshooting electrical problems much easier and they've gotten quite inexpensive 10-20.00. If you aren't familiar with how to use one, then you should at least learn to use together a simple continuity tester, a test light probe and a 3-4' length of 12-14 ga. wire with a medium sized aligator clip on each end. With those three items you can track down just about any electrical problem on non-computer controlled vehicles.

 

Like the others I think you have a bad ground. This is why the light acts crazy. If you are sending power from your turn singal switch to the bulb it finds its way to the bulb but with out the ground, it back feeds throu the tail light circuit because they are connected inside the bulb on the ground side and finds a ground on the other light. So it works, So when you turn the parking lights on the ground it was finding throu that circuit is now lost and then it doesn't work. The tail lights can do the same thing throu the turn brake light curcuit. Hope this makes sense.

 

Ax,
thanks for your help. I think I will buy those cheap electrical testers.

57 Ford: from your plain explanation I really think it is a bad ground. Your description does make sense to me.

thanks, abe

 

They are easy to make as well if you are so inclined.

 

I had some what the same problem when I put the lights back on after paint. The light didn't have a good ground!

 

Thanks to all but specially to 57 Ford! It was a grounding problem. I removed the turnsignal, sanded the bracket to get any paint and rust off, did the same to the washer and nut that held the turn signal light fixture, put it all together and no improvement. So I put a wire from the stem and nut of the turn signal and ran it to a clean bolt that holds the spare tire cross piece to the frame. The lights (turn, tail, and brake) were brighter than ever and worked like they should!

Question: Is this OK for a long term solution?

thanks, abe

 

Yes it is. In fact it's a better way to do it than stock. I run individual grounds from all of the lights on my boat trailer and I rarely have a problem. Just make the connections permanent.

 

Yes, run a 12ga stranded wire with soldered ring or forked connector on the ends to the closest chassis member where you can drill for a self tapping metal screw. Use a star washer under the head of the screw to bite into the connector for extra insurance. Once it is working properly, dab a little paint over the screw to keep any corrosion away. Go ahead and do the other side while you are at it.