Stubborn electrical issue*****SOLVED*****

[67F100_rookie]

I’ve been struggling with a stubborn right rear turn signal/flasher. I’ll start with the fact everything else works in the lighting area except gauge illumination and that darn right rear turn signal/flasher. I’ve run continuity tests, swapped harnesses, voltage tests, swapped the whole rear light housing, bulbs, cleaned and checked all grounds, etc. Even the license plate lights work. What else can I do to try and get that light working? Any help would be appreciated.

[jzjames]

Did you get a good look at the bulb socket itself - with those springy contacts,- and corrosion, etc.?

[67F100_rookie]

Yessir...I took the whole housing and plugged it into the left rear and it worked there with the brake light, back-up light, and blinker/marker. I’m gonna run some temporary wire from the firewall connector to the taillight and see if that isolates the problem. Prolly just make a whole new bed harness.

[Busboy]

Get the wiring diagram for your truck on this site, trace down the particular wire at the turn signal switch and see if it is operating there, if so keep following the circuit out to the light assembly. My guess, and I never guess because these trucks are so simple electrically, is that you have a problem in the turn signal switch. But again, this is a place to start looking, Don't go and replace the t.s. switch unless your diagnostics prove that it needs one. This is a matter of common sense rather than throwing parts at it.

[Ranchero50]

Use a #2 pencil eraser and clean the terminals inside the socket.

[sargentrs]

Check out the diagram http://www.fordification.com/tech/wiring/68-23.jpg. The RH side comes from the LH side via the rear harness. If the sockets work when connected to the LH side it's pretty much a guarantee that the problem is in that harness. Check continuity from both ends of each wire in the harness and you'll find the break.

[cep62]

Did you ever check out the turn signal switch ?
I've seen where the back will flash and not the front and vice versa.
Does the brake light work? if so it's not in the rear harness.

[67F100_rookie]

Thanks guys for the replies. Brake lights do work. It's a DC turn signal switch I installed recently. I get power from the switch to the dash harness. Continuity from the firewall to the rears. I think it's isolated to from where the instrument cluster plugs in under the dash to the connector on the engine side firewall. It is an unmolested/original wire harness except for a trailer connection I removed and patched the splice areas and from where someone tapped into accessory power on the light switch. I also have the Fordification wiring diagrams blown up and posted on my garage wall. Took me a while to learn how to read it but I got it figured out...pretty much.

[sargentrs]

Connector "T" is the first break in the wiring after the TSS where LH and RH are separated. Prior to that what affected RH would have affected LH too. Wire #5 (orange-blue) and wire #282 (green) are the RH turn signal circuit so I would check #5 for voltage with the RH turn signal on and then #282 at connector H and work my way toward the rear along #282. If all that checks out, it's gotta be a grounding issue.

[67F100_rookie]

CHEAP DENNIS CARPENTER TURN SIGNAL SWITCH!!!!!!!! Before I lost my mind I decided to yank the aftermarket universal switch from my 68 shortbed in the back yard and plugged it into the one I’m working on......really...that easy. Sweet Jesus the lost hours/days.....thanks for all the help, fellas. Never assume because it’s new that it works....

[crazyhorse]

Mr Rookie, congratulations . I am glad you found your problem.

[Ranchero50]

Nice, it really is a pity that Ford can't yank their rights to say factory correct replacements since DC's quality has went so far down hill.