New member with a quick question

[JW355714]

Hello,

My name is Joe and I am from upstate South Carolina. My truck is an 86 F150, long bed, single cab, 4WD with a recently rebuilt NP435 (Greatest transmission ever, and you can’t change my mind). I bought the truck with a 302 out of a 1990 Mercury Grand Marquis in it and the wiring due to the motor swap is…interesting to say the least. Currently my only real issue is that the turn signals work great when no lights are on, get slower when the running lights are on, and don’t work at all when the headlights are on. I knew the truck was going to have electrical issues when I bought it a few years back, but it ran and drove so I just ignored the electrical issues until recently. I’ll spare everyone the long painstaking details, I started with replacing all of the lamp sockets all the way around (some of them were melted), and tearing out the trailer wiring harness that was crudely spliced into the wiring harness for the rear lights and creating proper grounds for the rear lights. Since then the turn signal switch and headlight switch have been replaced due to corrosion and wear along with the turn signal flasher and hazard flasher. All of the lights are now much brighter and the turn signals flash much quicker than they did before I started this monstrosity of a project, but still no turn signals when the headlights are on. Before I go any further with this project, a previous owner had installed on of the cheap aftermarket ignition cylinders from AutoZone and cut out a place on the dash below the instrument panel for it. I’m assuming the OE ignition system in the truck isn’t compatible with the engine, but I don’t know that for sure. I am not very good with wiring diagrams, but from what I can gather it seems like the turn signal switch connects straight to the ignition switch and thus the aftermarket ignition could be causing the low voltage in the lighting system leading to no turn signals with the headlights on? The voltage reading on the aftermarket gauge I have in the dash drops a whole volt when I turn the running lights on and another whole volt when the headlights are turned on. I’m hesitant to go any further given that the likely culprits have been replaced, so any insight would be much appreciated!

[Gary Lewis]

Welcome Joe!  Glad you joined.  

Where in SC?  I ask because we have a map (Bullnose Forum/Member's Map in the menu) and we can add you with a city or zip.

On the turn signals, I'd bet that your problem is the ground for one or both headlights.  In the schematic below, which is from the 1986 EVTM (Documentation/Electrical/EVTMs/1986 EVTM), you can see in the lower left that the left front turn lamp uses Ground 801, which is on the LH inner fender behind the headlights.  But if that ground is bad then electricity in the turn lamp will actually go through the other filament in the bulb and try to power up everything on that circuit, which is a bunch.  And those devices will work well enough as a ground for the turn lamp to come on - until you bring those other things on.

The other things are the the LF marker lamp and the LF park lamp, which come on with the headlights.  So when you pull the headlight switch on the turn lamp quits working.

That is a classic grounding problem.  So look for the black wire that is coming out of your turn signal lamp and follow it to the ground on the fender.  Clean that ground up, as well as the one on the right side, and I'd bet your turn signals work when the headlights are on.

[grumpin]

Welcome!

[ArdWrknTrk]

Welcome to the forum, Joe!  

I'd agree with Gary, that those are classic symptoms of a faulty ground.
We can try to help with the wiring, but it is one of the more challenging things to do over the internet.

[JW355714]

Thanks Y’all! I cleaned up the left side, but it has t made a difference yet. Hopefully the right side is what’s bad

[Gary Lewis]

I'm hiding and watching.  Let us know what you find.

[mat in tn]

I imagine one eye peeking through a keyhole

[ArdWrknTrk]

😶‍🌫️

[JW355714]

Well, it didn’t work. Hopefully some attached pictures show what I had versus what I installed.IMG_2552.jpegIMG_2554.jpeg

[Gary Lewis]

Did you clean up where the ground goes against the radiator support?  And it looks like there has been some re-painting.  Is the ground still on the engine going to the cab near the windshield wiper?  There's a grounding problem somewhere.

For a test run a jumper from the ground on the battery to that ground lug in the picture and see if that helps.

[JW355714]

Yes, there is an engine to can ground and a cab to hood ground. I don’t have anything that grounds to the radiator support however…

[Gary Lewis]

JW355714 wrote

I don’t have anything that grounds to the radiator support however…

That may be the problem.  Try running a jumper from the negative battery post to that lug in the picture.  If that works then your fenders may not be grounded to the cab and/or the radiator support may not be grounded to the fenders.

Ford did a really poor job of grounding the Bullnose trucks, and if body work has been done the bolts that were intended to make the grounds don't.  I have #2 ground wires from the cab to each fender and from the fenders to the radiator support.

[JW355714]

I added a fender to radiator support ground, but all I had on me was 16 gauge wire. It didn’t seem to make any difference. If that isn’t big enough wire I’ll have to go get something a little bigger. Also, I’ve attached a couple of photos to show y’all just how butchered this wiring really is…IMG_2517.jpegIMG_2504.jpeg

[Gary Lewis]

The wiring is butchered.

As for the wire, #16 should be large enough to get a difference.  But did you put a jumper directly from the battery post to the ground for that light?  That is really the test you should do.

[JW355714]

Sadly, the jumper test did not improve the blinkers function. Honestly, I went for a drive after work today, and I love driving the truck so much I’ve decided I’m going to just enjoy it and drive it with or without blinkers for the foreseeable future.

BTW, I’m in Williamston South Carolina if you want to add me to the member map!

[Gary Lewis]

Sorry the jumper didn't do the trick.  I'm still convinced it is a grounding problem.

Anyway, on a positive note you are now on the map.

[BigBrother-84]

JW355714 wrote

[...] I love driving the truck so much [...]

Sir, I fully agree!

My wife and I did a 8500 miles road trip in US last summer, with Big Brother.
Some of our friends asked how we did that, without any comfort.
I swear that we never suffered, it's so cool to drive these truck.
That's what I call "driving".

If only they could drink a little less...


Welcome to the forum!

[JW355714]

The world just looks better when you’re observing it through the windshield of an old ford truck, doesn’t it?

My wife asks to take a ride in our truck, Nick named “black Betty”, almost every weekend! South Carolina might have some of the worst roads in America, but that old single cab with a plush bench seat rides great.

I have the “quad shock” suspension in the front, which may or may not have something to with the smooth ride. We are really looking forward to road tripping her to the mountains soon!