Here's a link with some diagrams. Page 48 has the brake/turn lighting. 46 has the back-up lights. Page 40 the marker lights.

Lights: - ???Gary's Garagemahal

 

KR98664 -
Sorry for the panic.
I bought the truck new in 1986 and have used it as my "car" since. I have done no "mods" to the truck. There was a period of about five years when I drove it very infrequently. Following that, I had both gas tanks replaced, the fuel filer, fuel injectors, distributor, and plugs replaced. Oil has been changed every 3000 miles. The lights have worked fine up until now.
After noticing the right tail light problem this morning, I replaced the bulb with a new one but it still did not work.
I did get under the rear of the truck to "look" yesterday and found a "T" coupler in the rear wiring harness. The "T" coupler has a four-prong trailer light connector coming off of it but it must have come with the truck as I did not add it. Yesterday, I did unhook that "T" coupler, blew the dust out of it and put it back together.
I appreciate your attitude. Thank you.

Franklin2 -
Please see my comments above to KR98664 regarding the "T" connector. Maybe I re-connected the "T" connector wrong but I recall it only went together one way. I will look again. Thank you.

 

Franklin2 -
Thank you for the diagrams. I should have mentioned that I did replace the trailer light relay a couple of days ago with an Autozone part. One of my thoughts right now is to replace the new headlight switch and the new trailer light relay with the old parts since it seems the problem was the brown/white wire connection, not the headlight switch or the trailer light relay. May be a waste of time but I think I will give it a try.

 

The small box under the dash with the 3-wire connector is a timer that turns on the EMISSIONS dash lamp every ~50,000 miles, you're supposed to bring the truck to the dealer service department for maintenance.

There aren't many pictures anymore and some of the displayed text isn't supposed to be there but here is some stuff on that timer box:

https://www.ford-trucks.com/forums/1...s-light-2.html

I agree with the other guys, look at the trailer wiring T connector in the back and the bulbs.

It's good that you saved the old parts!!! Changing ONE part at a time then determining the effects is a great way to go, you can un-do your change(s) to get things back to how they were in the event something is (more) wrong.

 

Good information. Thank you.

 

THANK YOU ALL!!!!!

It is a little difficult to see in the picture of the rears but the left rear and license plate lights are working.
I still have to hook up the speedometer cable, mount the instrument cluster and reinstall the trim.;l Hopefully I can complete these without causing any damage.
I am reasonably certain that the right rear tail light being out and the erratic turn signal behavior described in my post this morning was caused by me reassembling the trailer connector incorrectly. The trailer connector is tubular shaped and does have a small nub on the male side and a corresponding groove on the female side. However, the plastic housing has softened and allowed me to assemble the two pieces without aligning the nub and groove (it was dark and I was working with a flashlight). I took the connector apart this afternoon and was then able to see the nub and groove and reassemble the connector accordingly. All lights then worked correctly. I plan to complete this job very early tomorrow morning and will then post again. In the interim, THANK YOU!

 

Once everything is working, I suggest you put some electrical connector grease in at the least all the "outside" connectors....

 

Glad you got it working, tgun.

Yes, that electrical connector grease (dielectric grease is what it's called, or smth similar) is a good thing to use in exterior connectors to repel water, Ford originally used a brown/yellow, waxy-like substance for that purpose but you can get the dielectric stuff at most any parts store.

 

Glad to hear you got the lights working. Pat yourself on the back for finding and fixing the problem.

One question, though. What's with the reflection in this picture? Some kind of yeti finally captured on film? Or is it some homeless guy asking for money to squeegee your windows? Either way, be careful out there.

 

Dow Corning #4 is my favorite. Theoretically it should last forever, but once the shelf life expires, my employer has to discard it, so we get it for free:



I use it on all exterior wiring connections and bulb sockets. Makes a great dessert topping, too.

 

Vjsimone - Good suggestion.
Ctubutis - YOU gents got it working, I just provided the hands.
Kr98664 - Thank you for the pat but see my reply to Ctubutis. Reflection is Tgun aka Tom. Checking on the Dow #4.
Got to finish the job now - will post when complete.

 

All parts reinstalled. Test drove the truck and all exterior lights worked properly. Nice to have light on the instrument cluster again. However, the oil pressure gauge, tachometer, and right turn signal indicator on the instrument panel do not work. I expect the turn signal indicator is a loose/bad bulb but am unsure about the oil pressure gauge and tachometer. The large plug that inserts into the back of the instrument panel has numerous wires and I wondered if two (or more) of them could have pulled out / broken off similar to the way the brown/white wire broke off. Any suggestions? Thank you.

 

The brown/white wire burned off, it did not break off. Just to let you know, that has been a problem with these Fords, too much load on that wire. Hopefully when you fixed it, it has a better connection there. If it's still iffy, it may happen again. If it does, you have options.

On your oil pressure gauge, go out and find your oil pressure sending unit on the engine. If you have a 302 or 351w, it will be on the driver's side front of the engine, down very low behind the power steering pump. It will be a large round can very near the oil filter with a wire going to it.

Take this wire off, and with the key in run, engine off, take this wire and ground to a good clean piece of metal on the engine somewhere. Get someone to watch the gauge when you do this, it should start moving and swing full scale. Then take the wire off the ground, the gauge should swing full scale the other way. If this works, then the gauge and the wiring are good, your sending unit is bad and needs replaced.

Not sure what could be wrong with the tach. The tach on my 86 ranger did not work, so I thought. I then looked closer and found the needle had broken off, the tach did work but it didn't have a needle arm on it. I took a wire tie and cut it, and then super glued the cut wire tie to the center post and it has worked fine ever since.

On your dash indicator, you are correct that is probably a poor bulb connection. You need to take the cluster out and clean all the circuit board connections with a pencil eraser, and pull the bulbs in and out of their sockets several times to clean the connections.

If you also have a problem with your instrument cluster lights being a littl dim and hard to see at night, you might want to consider also take the same pencil and poking out the colored lenses for the lights. These get old and cloudy with age and will not pass light very well. I just let the bare bulb shine through, but most guys go buy colored bulbs and install them.

 

OK. Will try the steps you describe. Thank you.

 

We removed the wire from the oil pressure sending unit and connected it with a ground wire to the frame, turned the key to the run position, and got no movement on the gauge. Seems I am going to have to remove the instrument cluster anyway so is there anything in particular I should look for when I have the cluster out? Thank you.