Difficult turn signal problem

[68fe360]

When my head lights are off and I try to signal a left turn my driver side signal will flash the front light, both rear lights, and the dash lights. When the head lights are on the driver side signal does not work all, but the indicator stays on until disengaged. The passenger side works fine. When I step on the breaks and the headlights are off the dash lights come on.

This one has me banging my head. Any help would be great!!!

Hear's the trucks details and things that have been or checked.

1968 F100 360 with 3 speed
Items changed
1.) Flasher cans
2.) Turn signal switch ( new not used, It had broken pieces so I replaced it)
3.) Front end turn signal light, and head light grounds cleaned, or redone.
4.) Rear turn signals ground cleaned or redone.
5.) Brake light switch checked for shorts and operation
6.) Head light switch replaced ( it's was original and iffy)

Will

[cep62]

You have grounding issues.
Make sure all the ground wires have a good connection.
Sometimes the sockets get corroded and need cleaning.
If you're diagnosing a bad ground get a long wire with alligator clips , and hook to the battery ground ,
then you have a good ground for testing.

I see you did some work but make sure you have a good ground from the battery to the rad support and from the engine to the firewall.
and the bed to the frame.
Bolting down will work ,but rust and paint will hinder the connection.

[cep62]

And another thought.
I've seen where something gets bolted down like a cross member or trailer hitch, and some wires get pinched .
That tends to redirect the electrical current.

[68fe360]

Yeah I have been through all of the grounding points, and they are either fine or I fixed them. The up side is that my head lights are now brighter! You some times don't notice them getting dim slowly over time. One the first things I did was the grounding points and clean up the sockets. I don't think it's a hrounding issue

I made sure I did not pinch any wires while putting the grill back on. I think a hot wire from maybe the head lights is shorting to some thing else.

When I measure voltage at the driver side signal socket, I get the proper flashing of 12 volts. As soon as the head lights are turned on I get a steady 7.5 volts. I'm not sure if that helps give any clues or not.

I have been all over the electrical schematic, but the ones for 1968 kind of suck. I'm used to engineering schematics, and I'm having a hard time using these to track down which area could be the source of the short.

-Will

[68fe360]

Well I think I narrowed down the area of the problem, the rear tail / signal lights. Since there is a separate 2 pin connector for the rear I disconnected it and tested the system. The front's work fine with the head lights on and the rears disconnected. So the fun part is getting under the truck in 28 degree weather. I have to do my safety inspection by Wednesdays, and it's my only vehicle for a month or 2. Fun fun fun!

[68fe360]

Looks like I found the problem. Stock the truck came with the barden bumper which has an old style 4 pin trailer outlet. The P.O. installed a some what newer 5 pin outlet using
In line compression splices tapping off the original 4 pin connector, and a hockey ground 16 guage ground wire tied to the bumper with a small screw. The ground was sound corrosion wise, but when I lifted the outlet cover of the original 4 pin connector, the left side pin had white battery type corrosion all over it. This indicates that the connectors insulation had failed and it was shorting to ground and to right side rear running and signal light. This is why I would get 7.5 volts when the head light was on.

Once I clipped the leads every thing worked as it should. I plan on making my own wire harness in the near future. So I'm just going to cap these wires for now. New trailer connectors will be installed at that time. If I need one before then I will wire it up with new wires and correctly soldered connections.

Lessons for any one else trouble shooting the a similar issue.

1.) If grounds are OK disconnect you rear lights at the turn signal switch. This will help narrow down the problem to the rear or the turn signal switch forward.
2.) Old insulation at connectors can fail over decades. Eliminate connectors one at a time to pin point the problem child.
3.) If you see in line is spliced or crimp connections. Either test them or replace them. After market crimp connections suck, specially when exposed to the elemates. No snow or salt use in your area will help them last longer. I hate these things and redo them with a properly soldered connections and marine grade heat shrink when ever I find them. Even road vibrations will cause crimp connectors to fail or slice through the wire. Learn to solder at that correct temp, and all of the flux will be pushed from the connection and wire. This ensures no voids for corrosion to set in, leaving you with a highly reliable and long term connection. There is a reason crimps are not used on air craft. To low of a heat and you will have voids. To high and you will corrode the wire or connection before it is soldered. Remember that soldering is a type of welding and must be done correctly to be reliable. Like most things in life short cuts (Crimp connectors) and rushing the job will only ensure failure.
5.) The most important!! Ensure you use the correct guage ground wire for the current on the circuit. There are many websites that can assist in determine the correct guage and size of fastener to use.

Will