First off hello,
Im new to Rangers and Fords in general (GM/Chevy only till now) Mostly had s10's and blazers and know all about thier goofy issues so im not new to diagnosing automotive issues.

Anyways heres what i got:
2001 Ranger Edge, 3.0v6, 2wd, 5 speed, does have a 7 pin trailer harness but only 4 wires going to it, factory fogs with pass side broke (darn rocks), owned it about a week - been fine till now

Heres what ive last done: (it worked fine till i did this stuff)
Put new headlight housings in due to old ones being yellowed.
put in new headlight bulbs at that time
put in one new one used park/turn bulbs as well
i have used the hazard switch a few times and felt "gummy"
replaced front left side marker bulb as it was burnt out
put the spare tire back under the truck
replaced both license plate light bulbs

Heres what its not doing:
Key out all switches off:
Press brake - only rear brake lights (all 3 of em) come on and go off with pedal.
left turn signal on brakes still work normal
right turn signal on brakes work normal
hazard activated - the indicators blink and 3rd brake light responds to brake pedal (is it normal for the rear main brake lights to continue to flash with brake on? GM they stay steady...)

Key on/running:
everything works as it should - turn signals work, brake lights work, turn signal and brake lights on both work as they should hazards flash etc.

Heres where it goes screwy with parking lights or headlights on:
Key off parking light switch on:

Brake lights (all 3) light up
left turn switch on - left rear brake light goes out but no flashing - other 2 brake lights steady on.
right turn switch on - dash indicator lights up solid, center and left brake lights go out, left rear park light stays on, right rear brake light still lit and front turn light is lit steady.
hazards on turn switch off - both dash indicators light up solid, all 3 brake lights on steady no flashing front turns both light up solid.

key on parking lights on:
all 3 brake lights still on
left turn switch on - left turn signals blink (front and rear and dash indicator) the normal steady pace, other 2 brake lights stay on.
right turn switch on - all 3 brake lights on, front turn on solid, dash indicator on steady.
hazards still on steady along with dash lights

I unplugged the front indicator bulbs thinking thats the last thing i changed but no help besides the left turn with parking lights on rapid blinked indicating there is a bulb out.

I have cycled the hazard switch 50 some times as the first or second time i used it they stayed steady till i cycled the switch again - didnt think much of it as its pretty normal for GM crap to do this.

So from my past experiences with s10's the turn signal/ hazard switch combo in the steering column is usually the culpret with flaky turn/brake light issues but since the truck works normal with the parking lights off im not leaning towards the switch yet as i dont think the parking light circuit does anything with that switch. I read where the brake light switch can get shifted off the pedal and stay on - mine work normal without the parking lights on so i doubt thats it. I read where the trailer plug can cause issues so i got it down and it seems ok. I pulled pushed twisted it and didnt notice anything with the brake lights no major corrosion or nicked wires.

It has been raining since friday night so the truck is thoroughly soaked. I know the windshield and rear window leaks (i havent driven it since friday afternoon) and i read something about a ground behind the left foot kick panel by the parking brake mechanism that can cause issues but haven't checked there yet.

What do you guys suggest? To me it seems like its back feeding somewhere somehow through the brake circuit...Any common issues? I will check out that ground area tomorrow.

 

EDIT:
Just cleaned that ground behind the kick pannel - looked pretty good but removed and cleaned with sandpaper till shiney metal. Still no change in light issue.

More thoughts after studying the electrical diagrams: only area where the brake lights and parking lights come anywhere near each other is the trailer harness. Gonna fine tooth comb that tomorrow for any nicks and scrapes. I need to replace the connector anyways.

 

Looked this morning and found the brown wire in the back of the harness had corroded off. Thinking great found the issue i pulled it fully out and brake-lights still on. decided if one is corroded the others are close so i cut the entire plug off (someone put a 7 pin socket on it with the usual 4 wires to it - i need a flat 4 connector anyways) separated the wires and brake lights still on...I pushed and pulled on the bundle up underneath and no flickering or change in anything. Will have to lay under there tonight and have a look unless someone post up other issue areas.

I did notice when i pressed the brake with the parking lights on they get a hair brighter. Not by much.

 

Ahha! found the SOB problem spot. I have no idea how but the wire loom rubbed thru the plastic and into the rear light wire harness right next to the spare tire. completely rubbed thru the green and brown trailer harness and started in on i think a light blue. Just taped everything up for now till its not 38*f. I will cut solder and heatshrink every damaged wire when i install a new trailer harness. Meantime i tore the radio out chasing an old oil psi gauge illumination light. Discovered every solder and electrical tape job the tape turned to dust and bare wires out and about. Cut and soldered and heatshrunk all that.

Now all the lights work when they should!