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Let me first apologize. I've read a ton of threads, looked over several diagrams, and replaced quite a bit of parts before posting this but here I am.
I've got a 78 F150 custom 4x4 4spd manual with a 351m that I've been working on for about a year. This forum has already been tremendous help. I've replaced bulbs on all the signals and side markers, new fuses, replaced both flashers, new turn signal switch, and replaced 3 of the 4 turn signal sockets. I started out with no backup lights, brake lights (running lights worked but did not brighten for brakes), no hazards, and no turn signal lights. After replacing all of the parts, I have hazards (headlights on and off) and brake lights but no turn signals. The lights stay on but no flashing. I've swapped around the flashers and both will work the hazards. I'm wondering what my next step should be? The ground on the engine block and both rear signals seem ok.
I do have a few stray wires that the po seemed have messed with (pictured below). He used a couple of wirenuts but they seem to be feeding the radio. I personally prefer to solder.
so when you turn on the right turn signal, both front and rear signals are on bright but don't flash (and vice-versa for the left side)? and all 4 bulbs flash bright when the hazards are on?
if the pull the turn signal flasher while you have the left of right turn signal on, do both front and rear bulbs go off?
Not really. It's changed a bit as I have replaced parts. Currently, with headlights on or parking lights on, nothing happens when I move the turn signal switch. With the brake depressed and the brake lights on bright, when I turn the switch right, the right rear light dims. When I turn left, the left rear light dims. The front doesn't change. The hazards work like normal with all lights off but work very slow with parking or headlights on.
I have the same model (300 motor) with similar issues. The truck I am working on is in Louisiana and I am in Texas. It seems like each time I go back to work the problem changes. As of this weekend I had everything working except rear left turn signal. I didn't think to check brake lights.
The trouble shooter above should help.
If I get it all figured out, I'll post.
I have replaced:
all sockets
flashers
installed LED bulbs.
checked/cleaned all grounds.
Still trying to figure this one out. I've got voltage at the flasher, at the turn signal harness (both sides), voltage on the left prong in the turn signal when my lights are on, and fluctuating voltage on the right prong in the turn signal socket when the turn signal switch is on. I'm assuming that's what I would see on a multi meter at the socket when the turn signal lever is engaged, right?
The only thing I can thing is to replace that final socket and maybe the flasher is incorrect. Both work on the hazards, neither works on the turn signals.
Finally got this one fixed and another lesson for those who happen upon this thread.... replace all of the cheap crap up front. I must have miss understood the fuse diagram as the writing on the fusebox is pretty faded and mostly illegible. Apparently, I kept testing the wrong fuse but when I ran the light over every fuse, one of them struggled to pass voltage. I slipped in a new fuse, thinking "ahh at least something else will be fixed." I turned the truck off, screwed the turn signal lever back in, switched it down, and whala.. the dang things worked.
dlburch - I appreciate the troubleshooting guide. Generally the right answer is right in front of your face.
Reverse lights 101 from a fellow member: When the trucks came with a manual trans, there was a dummy plug used to bypass the NSS switch. I've never been able to come up with a part number for the dummy plug. To bypass the automatic set up:Unplug the switch and discard or ignore. There are four wires in the harness plug, two each, red w/ blue trace and black w/ red trace. Run a jumper between the red/blue and red/blue, do the same for the black/red.That completely bypasses the NSS switch. Your truck will now startand the back-up lights will be permanently on. Now on to the backup lights. In the engine compartment is a little U shaped jumper wire. It'll be located on the drivers side splash pan, just in front of the firewall where the wiring harness comes through.Unplug the little jumper, this will shut off the back up lights. There should be a back up light switch on the trans cover. Run two wires from the switch to the two wires that were jumped. This will get your back up lights working again. Just a note, you could make a jumper plug out of the NSS. Cut the switch off the harness and splice the two pairs of wires. I just hate to cut these switches up. New, they're getting pricey.Here's the little jumper in the engine compartment. EDIT: If you don't care about the back up lights, just jumper the red w/ blue trace wires. This will by pass the NSS but the back up lights won't work.
good work!
