I didn't see any trailer wiring. I'm actually surprised that the previous owner wired it incorrectly in the first place.

What would happen if I used a jumper wire from the R/W wire from the hazard flasher to the LG wire for the Brake On/Off switch?

Since the hazards work when the brake is applied, what I was thinking is that once the hazard switch is manually activated, it would send an electrical signal to complete the brake switch circuit. (But of course my electrical systems knowledge is minimal at best!) I'm just trying to think of an easy way to 'fool' the brake switch to be on when the hazard switch is on (but not vice versa).

 

The hazard flasher is hot all the time. It's always ready to work and when it does, it flashes, it's not steady power you need to send a steady signal to the brake circuit. Just like the turn flasher, it sits there any time the key is in run, and as soon as a light bulb load is applied, it starts flashing.

P.S. Unless a flashing brake signal would work? I dismissed this but maybe it would work, you would have to try it. And if it did work, you might have to put a diode in the jumper line to let the voltage go from the hazard to the brake circuit, but not let the brake circuit go back through to the flasher circuit. Sort of like a check valve.

 

I got the new headlight switch today. Unfortunately no good news. It is still blowing fuse #10. So I tore it apart further to no avail.

I unplugged the entire body wiring harness. Still blew the fuse so I moved inside the cab.

Tested that fuse box #10 is hot at all times. It had 2 wires - Tan/White and Lt Green/ Red. I tested that the Lt Green/ Red also had power at the brake pedal. (Brake lights were working so didn't think that would be the problem.)

I pulled the fuse panel and headlight switch out so I could trace wires. Unwrapped the wiring harness and traced the Tan/White from the fuse panel to the headlight switch. Tested that the terminal (B2) at the headlight switch is hot at all times. It has 2 wires Tan/White and Red. Didn't notice any melted, exposed or frayed wires.

Per the conversation above, I still thought the Tan/White might be the culprit. I took the connectors out of the fuse box and headlight switch and ran a new wire between the two. It didn't blow the fuse, but it caused a spark and little smoke from the new headlight switch. (Did I ruin it?!)

So now where do I look or other things to unplug? I've already pulled any connector I could find apart and cleaned with electrical cleaner. I don't even know what color wires I'm supposed to be searching for to find a short. I'd hate to start cutting all the wiring harnesses apart under the dash trying to find a needle in the haystack. This is so frustrating!

 

Well, since I have everything torn apart I figured I'd give it a try. I stuck a piece of wire from the hazard switch to the (disconnected) brake switch. Sure enough the rear hazards started flashing! So now I have to find a diode before wiring it up. What size diode should I use?

 

This diode should be big enough.

https://www.radioshack.com/products/3-amp-400v-diodes

 

If the fuse doesn't blow until you turn the headlight switch on, then the problem is going to be with the brown wire that leaves the headlight switch.

 

I'm about fed up.
I purchased the diode; doubled checked which wires from the hazard switch and brake switch; and wire it up with diode in place. I press the brakes and the brakes come on. I press the hazards and nothing at the rear. I touched the new wire with diode and it is burning hot with electrical smell. Great...

I disconnect the new wire. I go back to the jumper wire that I tested it last night and can't get it to work at all. To make matters worse, I can't get the right side to light up at all - brake lights or turn signals. I pull the harness and it is getting power back. I test the right tail light wire and nothing. So now the new converter box isn't working either. I have to cut up the newly wrapped harness and all the connections. I can't even put it back to original because the wires have been removed.

To recap - I started this project with an electrical backfeed through the dash lights and now have a short I can't find; a burnt light switch; a burnt converter box; and cut wires all over.

 

What engine are you running? A late model fuel injected ranger engine and trans?

 

Doesn't blow until parking lights are pulled on. Headlights still work. I literally have the dash pulled all apart and can't find the problem.
Is there a wiring diagram from the head light switch?
From what I recall, when turn on the running lights:

• Front parking lights (signals and hazards work)
• Rear parking lights
• 2 instrument cluster lights
• Original ashtray light
• One HVAC panel illumination light

 

Yes, 4.0 fuel injected - auto trans.
It does still run. I started it today to check a new mechanical gauge that I installed.

 

Second diagram down in this link is your marker light section of the headlight switch.

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

 

I checked those external locations. I was trying to locate other areas in the cab or engine compartment to check.

-I noticed that there is a 'warning chime module'. I've never heard anything chime, but I unplugged it just to see if it may be the issue. Fuse still blew when pull headlight switch to running light position.
-Since it still happens with the body and rear harness unplugged, I ruled out the rear lights. Plus, there is new wiring back there.
-I visually inspected the front parking lights (couldn't find where they would unplug and they are wrapped in a wiring harness). Signals and hazards work so I don't think it is a ground issue at the front lights.
-Traced the tan/white wire and no visible damage. (Using a jumper wire to bypass the tan/white didn't work out so well.)

With regards to the taillight converter, I spoke to technical support for Tow Ready (current unit) and Curt. Tow Ready thought it was an issue with the converter since it is not sending power to the one side. CURT recommended a powered converter (more expensive, of course) so I have another one on order. With a bunch of different brands (Reese, Tow Ready, Curt, Draw-Tite, Hopkins, Tekonsha, etc.) and multiple model ratings (2amp, 5amp, 6amp, 7amp, 8amp), I had no idea what might be better. I'm hoping the new converter will last longer than 3 days.

 

You can't assume this. The signals and hazards are a totally different circuit. You need to leave no stone unturned, your front marker lights and wiring are a stone you have not turned over yet. I know you said it's going to be hard to diagnose, but keep trying. That's the only thing left on the circuit correct?

There is nothing on this circuit inside the cab except possibly the radio. The brown wire is the one you are concerned with. Sometimes they run the blue/red to the radio for the button illumination, but they also run the brown to the radio to trigger the digital readout to dim when the marker lights are on.

 

Uncover that brown wire leading from the headlight switch, and if you have to cut it when you reach a splice, do so to try and figure where the problem is located.

 

The plot thickens...
So despite my Dad telling me not to take apart the front park lights ("they won't be the problem", I did so anyway. What do I have to lose at this point, right?! I just pulled the bulbs out (they appeared fine) and tried the headlight switch. Dash lights come on, no blown fuse.

So I replace the bulbs and try them. This time they come on (no blown fuse) but are still acting up. I ran through some sequences to hopefully identify the potential issues. (FL Front Left, FR Front Right, BL Back Left, BR Back Right) Problems highlighted in red.

Brakes: FL - None | FR - None | BL - On | BR - On but Dim
Parking Lights: FL - None | FR - On | BL - On | BR - On
Hazards - blinks normal: FL - On but very dim | FR - On | BL - On | BR - On but dim
Left Signal - blinks very slowly: FL - On very dim | FR - On very dim Shouldn't be on | BL - On | BR - On but dim Shouldn't be on
Right Signal - blinks normal: FL - None | FR - On | BL - None | BR - None

I (visually) checked the grounds:
-There is a new ground from the frame to block.
-Inner fender on both sides have a small ground that comes out of the wiring harness behind the front radiator support.
-There is another larger ground on the driver's side wiring harness that goes to the negative battery terminal.
-There are 3 grounds that are on the driver's side inner fender by the master cylinder.
-There are grounds going to both tail lights; runs through the truck's wiring harness and through the converter box.

Thoughts? I have access to a multi-meter but not exactly sure how to check grounds, voltage, etc.