Hoping someone can help out. I'm at a loss.
1994 Ranger drivetrain/wiring in a 1954 F100.
Long story short: Brake lights were not working. Pressing the brakes resulted in the running/dash lights turning on. After days of testing and checking, it seemed that the rear tail lights were not wired correctly. I mocked up the driver's side to test and everything seemed to be correct. I got new tail lights, wired them up, and now several new problems. Brake lights and 4 way flashers work as they should.

1. Left turn signal or right turn signal result in both tail lights flashing. (This didn't happen before.)

2. Biggest issue I'm having is it is blowing the running lights fuse (#10). If I press the brakes or use turn signals, the fuse is fine. However, as soon as I pull on the running lights, pow. (This didn't happen before.)

-I disconnected the entire rear harness. Still blows the fuse. (So I have to believe the problem is not the new tail lights?)
-I used an air hose and electrical cleaner on the fuse box, light switch, dash board, turn signal switch. Still blows the fuse.
-I disconnected the turn signal switch entirely. Still blows the fuse.

It is very frustrating as I did not have a problem with the running/ dash lights and everything was working a day ago. I didn't change anything else/ drive it anywhere. The logical thing was to undo the changes I made (tail light wiring). However, even when I tried to backtrack, I'm still having issues. I went through 2 packages of 15 amp fuses, cut out brand new wiring, and spent the entire day trying to clean and trace wiring.

Is there anything else I should try? How can I test where the short is?

 

I'm confused about the fuses and what could cause it to blow.

#10 fuse (keeps blowing): Turn/Stop/Hazard Lamps, High Mount Stop Lamp, Speed Control Amplifier, Warning Chime Module. Power supplied through fuse 2 of engine compartment fuse/ relay box.

Instrument illumination is #13 fuse. Power through fuse 2 of engine compartment fuse/ relay box, fuse 10, and main light switch.

When I turn on the main light switch, it blows fuse #10, not #13.
-Stop/Hazard Lamps work correctly.
-Turn signals are not functioning correctly, but does not blow the fuse when turned on. I disconnected the turn signal switch and it still blew the fuse.
-It blows the fuse even when the rear wiring harness is disconnected. When I had the brake light issues, I was able to test each pin in the wiring harness including the running lights. This is how I was able to determine how to re-wire the tail lights (when each terminal was hot for brake, turn, running lights, etc).

FYI - High mount stop lamp is not in use.
I'm not sure what the speed control amplifier looks like/ where located.
Warning chime module - I disconnected it, sprayed electrical cleaner and plugged back in. Did not open the module.

Going nuts here trying to figure this out.

 

Here are some diagrams. If you can't read them we will help you. Think of it like a big tree. The base of the tree is the battery. You have large branches off the main trunk, that will be the large fuses in the underhood fuse box. You will have smaller branches off the large branch, that is the smaller fuses.

If one fuse blows off a small branch, it will not affect the other branches that are fed off the large branch. The only thing it will affect is the fused branches downstream if there are any.

Here is fuse 10 in this diagram. It shows the high mount stop lamp which you said is not hooked up. I am putting this in here just for reference. The fuse doesn't blow when you push the brake pedal, so we can ignore this as the problem. We need to hunt down that tan/white wire.

http://www.revbase.com/BBBMotor/Wd/DownloadPdf?id=43869

Stay tuned.

 

Here's another link with another set of diagrams.

http://www.revbase.com/BBBMotor/Wd/DownloadPdf?id=43870

In the first page in that link you can see the hazard flashers and the turnsignals. You can see at the top they are fed by totally different fuses, totally separate branches, not affected by the other circuits.

The second page down is where I bet we need to be. You can see fuse 10, and you can see the tan/white wire. It goes directly into the headlight switch. The headlight switch is several switches hooked to one ****. The headlights are fed from a separate circuit, separate part of the switch. This part of the switch is for the marker lights, all fed by the brown wire.

Unfortunately, this is one of the most difficult circuits to diagnose You can see all the splices, this single circuit goes all over the truck. The only way to troubleshoot this is to do what you have done already, unplug certain parts of the harness.

You said you unplugged the rear most portion. Since you have had your hands all over this harness putting it in place in this old truck, you might have a easier time locating some of these plugs. In the diagram above, see connector 118? That separated the complete rear harness from the front. Can you find it and unplug it? Maybe then you can determine is the problem up front with those lights, or in the middle rear. You have already disconnected the very back of the harness correct?

 

After reading only the first several sentences of your initial report, you have an open ground in the lighting circuit. Find and repair it, then re-evaluate.

The blown F10 is probably due to an error in the changes you made trying to fix the first problem. Undo whatever you did until the short goes away. Buy a re-settable circuit breaker, it will save on fuses. Otherwise, use a meter with an audible continuity tone, you can listen for the tone as you disconnect stuff.

 

Thanks for the assistance!
I'm stuck in a blizzard so I couldn't get out to purchase new fuses / fuse circuit breaker today.

Tested the body wiring harness going to the rear:
Connector pins for the brakes, turn signals, 4 way flashers worked properly. (Didn't try running light as I didn't have any more fuses.) I did find 2 sets of brown and black wires going to the license plate light. One set were cut off and wrapped in electrical tape. When I plugged the rear harness back in, both turn signals blink with either directional. (The dash indicators and front signals work correctly.) I must have something crossed? How should the tail lights be wired? They are 1157 double filament bulb. (Ie. there is only 1 bulb, no separate turn signal bulb.)
Fuse Panel:
I found the Tan/White and Light Green/Red wires coming out of the back of the #10 fuse panel. I tried to trace the Tan/White, but it runs into a harness that is wrapped. I haven't found the Tan/White coming out of the firewall yet. (There is a whole bundle.) I didn't see anything melted or broken yet. Are you suggesting that cut and replace that wire anyway?

Head Light Switch:
It was a real pain to get the connector off. Once I got the switch out, some of the wire connectors and terminals are a little corroded. Is there a way to bench test it? Or just replace it anyway?

Short test:
I forgot to do the battery test to see if there was a short until after I took out the head light switch. I put the one end of the test light on the positive battery terminal and touched the probe to the positive battery terminal. Light did not turn on.

I spent the rest of the day checking to see if any wires were bare/ rubbing under the dash and cleaning anything I could find with contact cleaner. I had been fitting the heater controls in a custom panel so thought maybe something got pinched. But didn't see anything obvious. I can run more tests once I can make it out of the driveway to purchase a circuit breaker thing.

 

Look at the tan/white in the diagram again. It goes from the fuse to the headlight switch in the diagram. So it will not go out the firewall. Only the brown wire will go out the firewall.

Reading your last post it dawned on me what is wrong with your turn/hazards. Look at page 3 in this link. http://www.revbase.com/BBBMotor/Wd/DownloadPdf?id=43870. The brake switch circuit does not go through the turnsignal switch like a normal vehicle.

Your donor vehicle had amber turnsignals in the rear correct? If I am right, you are going to have to do some figuring on this.

1. You cannot put your turnsignals straight on the bulbs like you have them now. You are using conventional red brake/turn/marker taillights. Your vehicle is setup with separate amber rear turns.

2. To get around this you are going to have to install separate bulbs in the rear just for the turns, or you can buy a trailer adapter box at the store and wire that in place.

And you still have a short circuit on your brown wire somewhere. Make sure you did not hook the brown wire to any grounds in the back.

 

Ahhhhh....

I didn't build this custom truck, so I didn't realize the stock '94 Ranger had a dedicated turn signal bulb. The prior owner had running lights and brake lights wired together causing backfeed through the dash lights. Now it seems I've just reversed the problem, causing backfeed through the turn signals.

I debated about drilling and adding another bulb. But the 1955 T-Bird chrome tail light housings are round and I'm not sure that bulb would sit right. Ordered a trailer tail light converter. I think I'm going to build a new wiring harness for the rear so I know what I've got. It should only be:

1. Running Lights
2. Brake Lights
3. Left Turn Signal
4. Right Turn Signal
5. Backup Lights
6. Ground

Yes, there is still a short but I'm still not sure it is coming from the rear harness. When I disconnect the harness, the fuse problem remains. I'll re-trace that tan/white wire to the headlight switch. Got confused as the one diagram had "T/W to Power Distribution" which I thought meant it went through the firewall first.
Hopefully once I shovel 28" of snow, I can get to the auto parts store later.

Thanks again!

 

The diagram I linked to does not designate where that fuse #10 is located. I may have jumped the gun on that. Where is the fuse you keep replacing located? If it is in the underhood fuse box, then sorry you are correct, the tan/white would go through the firewall to the headlight switch. If the #10 fuse you keep replacing is under the dash, then it will not go through the firewall. I may have jumped to conclusions on that one.

I had a 53 f100 that I used one of those converter boxes on. It had the stock steering column with a clamp on turnsignal switch and separate turnsignals. But the problem was the switch only handled the turnsignals, and they had drilled holes in the fenders and added turnsignal bulbs, they were ugly.

I converted the front marker bulbs to double filament sockets, and used conventional rear red turn/brake/taillights in the back on each side of the bed. I mounted the converter box under the dash on the firewall, ran the brake switch wire into it, and the turn wires into the box. The box mixed the signals together properly, and then I ran one left and one right brake/turn wire to the rear, and one running light wire for both sides and the license plate lights.

 

Nope - You were correct! #10 is in the fuse box under the dash. I just didn't understand the diagram "See Power Distribution".

My front lights seem to be operating correctly with running lights and signals. (I plan on changing them to LED.)

You mentioned mounting the converter under the dash. I planned on splicing it into the rear harness and mounting it to the frame rail or under the bed. Is it ok to put it there?

 

If you can keep your connections dry. I believe the box is rated for mounting outside isn't it? You can wire it up temporarily to see if it's going to work, but the best way to permanently wire it in place is to slip shrink wrap on one of the wires, solder the wires together, and then slip the shrink wrap over it. The best shrink wrap to use is the wrap with adhesive inside it. When you shrink it, the adhesive will ooze out and seal the connection inside.

 

So I bought this tail light converter.



I spliced it directly into the rear harness. Both turn signals now work independently. However, the only thing not working is the 4-way flashers. (They still work on the dash indicators and in the front.) Thoughts?

With regards to the short - I had someone test the head light switch and it was not operating properly. I'm going to put a new switch in before re-testing the running lights.

 

I have never tried using hazards through the box. It may not support the hazard function. If that is important to you,the box may not be the solution.

Make sure the turnsignal switch is in the center when trying the hazard function, that may affect it. Activate the hazards and then get a testlight and probe the turn wires going into the box to see if they are flashing.

 

It's not critical, but after all the money and effort it is nice when things work correctly!
When the hazards are engaged, the rear harness gets signals to the 2 turn signals. I discovered that they only turn on once you press the brake pedal. I think since the converter is internally combining turn signal and brake, it doesn't recognize the hazards function until the brake is engaged. Without the converter, the hazards were working correctly.

This may be a crazy idea...
Is there a way to wire the hazards (located in the multi-function switch) to engage the brake light switch when turned on? Ie. falsely engage the brake switch without pressing the brakes. (But I can't have any backfeed to the mult-function switch every time the brakes are applied.)

I greatly appreciate the insight and recommendations as I sort through these issues.

 

I am not sure how you would activate the brakes unless you added a switch somewhere. The hazards are manually activated, your truck would need two actions to activate them, the hazard switch and the other switch. Can't think of any way else to do it.

I was looking at the diagrams again, I don't see it. But I have worked with some explorers with the rear amber turns, they came from the factory with a towing package. They had a set of wires going from the multi-function switch all the way back to a plug to hook a trailer up to. All I had to do was go to the store and buy a adapter plug that went from the factory plug back at the rear bumper, to a standard 4 way trailer plug. The factory ran these wires back from the multi-function switch, they were wired into the switch and acted just like a conventional taillight with turn/brake and tail all in one red light. So I did not need a converter box.

I thought there may be the chance your 94 ranger donor had a towing package option with it. If it did, you would have these extra wires going back there, and you could forget having to use the converter.