New to the site. I've been reading a lot about possible problems issues about not having the turn signal to work properly. Currently Head lights, parking lights, hazard lights, brake lights all work, no turn signals yet. First off I replaced the turn signal but nothing resolved. So I started checking the resistance on old and new turn signal to see if either one is working or not? Both have the same resistance with the turn signal in turn mode (Right turn & Left turn). So I've elliminated that potential problem. Next I do not have the horn hooked up, could that be a potential problem? Last I unplugged the steering wheel harness (6 plugs) and used a 12v power source to each wire to verify if the lights worked or a possible ground problem. Everything good to the lights and parking lights. Per the Fordification wiring diagram for 1968 F100 it only shows 6 wires going from the turn signal switch to the harness (connector). Horn wire (Blue-Yellow) is missing. Another question for everybody should the Emergency Flasher and the Turn Signal Flasher be the same model number or different. I replaced both with new thinking the old ones where bad. The original numbers where different but all part stores say there the same. Thoughts????

 

There are TWO different flashers located in TWO different locations. Both flashers are round with two prongs, but the 4 way flasher is a heavy duty type, as it has a louder CLICK

The 4 way flasher can be used in place of the T/S flasher (and was with Camper Specials & trailer tow), but the T/S flasher should not be used in place of the 4 way flasher, as it's a "weak sister."

1967/69 F100/350: 4 way flasher switch located on the inside of the glove compartment.

The T/S flasher plugs into the back of the instrument cluster. The 4 way flasher fits into a bracket that is retained to the backside of the dash w/a screw.

See parts catalog pic for location of switch and the two flashers:

 

So based on your thoughts I will try a heavy duty flasher but thoughts on where I might get one? Second I know where both flashers where just second guessing my self I that might be the problem

 

D1FZ-13350-A .. H/D Flasher (Motorcraft SF-552-B).

Myriad 1960/90's FoMoCo vehicles.

 

The emergency flasher was color coded green. Whether green plastic or green letters on a metal can.
The T/S flasher was color coded lt. blue.
Check the 14 amp fuse to be good. And clean contacts for it. If it's good then with the key on check for 12V in the orange/yellow wire at the T/S flasher. Circuit #8.

 

Check the connector indicated by a circled "S". That's your six-pin connector. The connector indicated by a circled "T" is also a part of the circuit. It connects the outputs from the TSSwitch to the Right and Left rear turn lights.
Not having the horn circuit hooked up should not impact the operation of your turn signals whatsoever.
It sounds to me like you have a break in wire #8 or wire #44 somewhere, possibly at the back of the connector that provides power to the Windshield Wiper Switch, possibly at two different pins on the Instrument Cluster Connector, possibly at the connector that goes to the TSFlasher or possibly the back side of the connector indicated by a circled "S" (specifically, wire #44 on that connector).
Assuming that you have a good TSSwitch and a good TSFlasher, there isn't much left.
If it's only the rear turn signals that aren't working, I'd suspect that the connector indicated by a circled "T" is probably disconnected.
The Horn circuit is probably the same as is shown in the 1970 master wiring diagram, Wire #1 (Blue/Yellow stripe). It wouldn't be shown as a part of the "Lights and Turn Signals" diagram, since it's neither a light nor a turn signal. It seems pretty obvious to me that it SHOULD HAVE BEEN included, due to the proximity between Wire #1 and the TSSwitch wiring.

 

Gentleman, appreciate all the help. It seems I never thought about circuit #8 and of course no power at the Flasher, so I also replaced the fuse thinking it was bad. No luck still. So I started checking if I had any power starting at the 14amp fuse. Nothing at all on either tab of the fuse. (All other fuses had power) So it seems now I need to remove the fuse panel and see if the back side wires are loose, disconnected, our burned. The fun beings round two. Thanks again

 

Before removing the fuse box I suggest checking power to that fuse. Notice in the schematic above power starts at the ignition switch "A" terminal for that 14 amp fuse. It's a black with green stripe wire. Circuit 297. Check the ignition switch to see if it's coming apart. Also check the wiring pigtail connected to the switch. See if heat has melted or deformed things. If all looks okay then check for 12V in the black/green wire at the switch. With the switch turned on of course. If no power it's the ignition switch or that wiring pigtail. If there is power then check for 12V again. Only at the fuse box this time. The same black/green wire. If there is power in that wire just before it enters the fuse box, and no power at the fuse, then remove the fuse box.

 

Gentleman - Since last time we spoke I've finally had time to check the 12V black/green wire at the switch (with switch turned on) and it has power. Plus changed out all of the fuses I have. Unfortunately this is becoming not overwhelming but ridiculous. I will check the six pin connector on circuit #44 and #8 again. Last suggestion - Is their a chance with the six pin connector I might have a wire in the wrong plug? Would this not make the turn not signal work? After a while everything you double check becomes a blur.