Tail lights
There is a stretch of highway here that is signed to the effect of running lights are necessary. It's a bad bit of country highway, maybe 20 miles that claim a few lives every year.

I changed the turn signal switch last year and this fixed my problem. Then one tail light quit working, that's when the brother in law helped, never thought to check function with the brakes applied.
I'm thinking a bad ground or connection might be the problem.
Number Dummy are you saying I can use the listed hazard flasher in place of the "weaker sister" turn signal flasher?
While we're on it what do we call the "non-headlights" that will activate the secondary filament of a dual filament bulb when the headlight switch is in the "pre-headlight" position?
"Ancillary lights?"

For the rear light issue look at this.
In the engine bay you have wiring harness coming out of the fire wall on the left side and runs down by the floor board where it plugs into the wiring harness going to the rear of the truck.
I would un-plug it there and take the rear harness (trailer connection) out of the picture. If you have everything working right at the plug then you know the issue is with the rear harness.
Dave ----
At the same time, make sure the bulb sockets are clean and free of corrosion and their ground connections are good.
User-added trailer wiring done in a haphazard fashion has been known to cause all kinds of weirdness.
After all of that, including the flasher, next place I'd be investigating is the turn signal switch. But make sure the base infrastructure is good, first.
1) Wait until after sunset, turn off any porch lights, etc., to make it as dark as possible. Then switch on your turn signals one side at a time. You may see some other bulbs light up dimly, but they wouldn't be visible in the daylight. If that happens, you've got a bad ground at one of the light assemblies with a dual-filament bulb.
2) Remove the flasher and rig up a jumper in its place. You will then be troubleshooting a very simple circuit consisting of a power source, a switch, and several bulbs in parallel. Trust me, this is WAY easier than trying to get a meter reading as the flasher cycles on and off, and of course any change in the circuit load (removing a bulb) affects the cycling rate of the flasher. Your jumper could be as simple as a paper clip. You could also crimp a pair of male spade terminals on the ends of a short length of wire. Or get real fancy like I did, and modify an old flasher by uncrimping the cover, jumpering the terminals together, and reinstalling the cover. Make sure you prominently mark a modified flasher so you don't accidentally reinstall it down the road.
3) As far as checking the old bulbs, I'd just replace all of dual-filament ones, even if they are the correct part number. A bulb's amp draw can change due to age, and that will throw off a thermal flasher's cycling rate.
4) Keep in mind your truck has 2 flashers on the fuse panel. The one on the aft side (facing the driver) is for normal turn signals. Originally this flasher was the thermal style, was NOT designed for the extra bulbs of a trailer, and would flash at a different rate if the load changed. You can change this to the non-thermal style if desired, but you'll lose the change in flash rate to alert you of a problem. The second flasher is for the 4-way hazards only, and is on the firewall side of the fuse panel. I think this one has to be the non-thermal style.
I've seen a lot of farmer work before, my luck there will be some aluminum foil and duct tape.
How do I find an open ground?
What did you do with your original hacked-up wiring, and what kind of state are you in right now?
Mostly sober

I didn't get under the truck except to take a peek. Saw there was nothing for the spare tire carrier and everything looks a bit mucked up and dirty so throughout the week, time permitting I will get under there and clean everything and start checking the bad side.
O, I did replace the flasher with the heavy duty one hoping maybe it just needed a bit more "umph" to no avail. Not a total loss for $5 as I can hear the clicker now.
Ford Trucks for Ford Truck Enthusiasts
I guess I'm not understanding.
I'm going to use the tester to make sure my connections to the frame ground are good?












