Ok so.... start from the top.
wanted to upgrade my 80 f150s lighting. Ordered really nice leds for all my markers, brakes and reverse lights. After i installed them my reverse lights stopped working. Pulled everything out and went back to stock. Still dead. May be my gear positon sensor on the transmission.
next, I installed new h4 housings and bulbs and replaced my right front marker light socket. Now when I turn my lights on the front marker don't light up, my front turn signals don't work and only the left one is super dim with the hazards on.
back in the early 90s my grandpa installed a 12v air horn. It honked its last honk so I replaced it with a new one set it up to be powered with my factory horn circuit like the last one was except this time I was using a relay. Well now my horn don't work. Using my power probe chaced it all the way back up the column and everything seems fine just nothing when I push the horn.

replaced my negative battery cable and the power wire from the solenoid to the starter. Truck starts right freaking now so that's good lol. Spent like 6 hours doing everything just for nothing to work now.

oh i replaced my right marker socket cuz when i turned on my lights the right turn signal bulb would light up too..


Any help? Im a mechanic and am pretty versed in electrical but old **** being so simple makes it hella confusing to me lol.

 

It sounds like the grounds are not grounding!
Start at battery to motor, motor to frame & motor to cab.
Out back run a 10ga wire from frame to bed.

Now up front under the hood there is a ground on each side by radiator fender that dose the head light, parking/ run light and turn pull them & clean.

The lights out back gave a ground behind the housing or a ground wire that runs in the harness and screws to the firewall inside by the radio.
Clean them all and retest.
Dave ----

 

I was planning on over grounding it anyways . But the **** of it is the only ground I touched was when I replaced the battery ground to the engine , cleaned everything and it's all tight. Seems like a ground issue but just weird symptoms

 

So all your lights were working fine, including the back up lights, you swapped out for the LED lamps and then you had problems?

I agree with Dave that checking and cleaning grounds should be done. You replaced one socket too. What are the conditions of the sockets? Make sure they are clean and solid.

Are you sure the back up lights worked before the swap? I've noticed that back up lamps are the first bulbs to go south on my truck. I've replaced them more often than any other bulb! Check the bulbs! Yes both can be bad at the same time.

Double check your fuses too.

 

Ok so checked the grounds they are fine. I'm using the same grounds for the relay harness. checked fuses like 4 times. There is only like 8 total fuses for my truck. After far as I know the reverse lights worked . 2 weeks prior a co worker told my my break light was out when I was backing up so im assuming everything else was working.
installed a new headlight switch today that I already had on order and still no change. I may try unplugging the h4 bulbs and see if that makes a difference. I don't think so but worth a shot. I got the hella +50 so maybe they are pulling too much amperage ? But my side markers work just fine. I gotta bring my multimeter home this weekend and poke around.

 

Since so many things are bad at the same time check your wiring diagram and see if they are all being fed by the same fusible link.

 

Checked the factory ewd I have and it seems that if it was a fusable link id have more random stuff also not working. The only thing everything has in common is nothing really. That's why this is such a pain. The lights are all parallel so one being out won't effect anything. And if it was a ground I'd also have more not working cuz it looks like the head lights and front turn signals ground to the same spot. Or at least that's how I read the diagram. Shouldn't be this complicated truck only has like 20 freaking wires

 

Well I guess your best plan is like you say, get the multimeter and dig in. Let us know what you find.

 

So iv been stealing at the ewd for the horn. The system is so simple its a pain in the ***.
so what I have found on the horn is, it piggy backs B+ through the headlight switch, runs up the column to the left post on the steering wheel (where the horn plugs in) when pressing the horn sends power back down to the yellow wire on the horn and ground through the horn.
I'm so used to new stuff where the horn gets power from the horn fuse , to the relay horn pad is a ground side switch and completed the circuit.
Donno why ford decided so much needed to run through the head light switch. No wonder they burn up so damn often . Gotta double check that im getting power at the steering wheel and move on. I'm starting to think I may have a spiral cable (or clock spring) that's on its way out causing all my funky issues

 

In 1981 the horn is fed from the same fuse as the cigar lighter. I don't have a 1980 diagram in front of me, but I would not think it would be that much different. The headlights have their own dedicated B+ coming from a fusible link and is not fused.

 

You may find this to be some help:

https://www.ford-trucks.com/forums/1...ing-guide.html


For troubleshooting, I highly recommend bypassing the two flasher units as described at the link above. It makes is a lot easier to do the basic tests for power and ground in those circuits.

Careful about digging too deep too fast, in hopes of a quick fix for everything. I'd pick a simple circuit, such as the tail lights, and figure that out first. Correct any faults you find, confirm the circuit now works, and move on to the next thing. You may have more than one active fault, and the only way to find each one is with careful, methodical troubleshooting.

 

That article was a huge *** help. Made me go check the basics. That i should have checked in the first place. So what was happening with my marker/turn signals was that bulbs that were good were now bulbs that are bad. Went to check everything at night like the page said. And when I popped my hood I noticed the right turn signal indicator blipped . Hmm weird. So I jumped the flasher and went to look at the bulb do the ol wiggle test. Come to find out the bulbs filament was broken but would intermittently catch contact and light up. Literally didn't think it would be the bulbs cuz were fine the day before. Or were they? Now just gotta figure out the horn situation.

 

As far as I know the 80/81 were exactly the same and they didn't really start making changes till 82 . ( that's why you never buy the first of any new vehicle) the lighter fuse is good so im wondering if it's a wiring issue after the fuse