2003 ford ranger: tail lamps not working when headlights are on!!

[iLoveMyExploder]

'03 ranger: tail lamps not working when headlights are on... SOLVED!!!

2003 ford ranger, tail lights issue.

my father in law just bought this truck a week ago and a problem has occured since purchase. he has no choice but to drive when it is dark because he leaves for work when it is dark, and does not get off work until it is dark again. and he works 50 miles from where he lives. so this issue must be resolved ASAP!! thanks in advance to those who respond, and huge thanks to whoever knows how to fix it and tells me!!

Issue:

when the headlights are turned OFF, the tail lights- running lights, blinkers, and hazard lights function properly.

when the headlights are turned ON- none of the tail light functions work properly, if at all. if the either of the left or right turn signal blinkers are activated, BOTH of the tail lights flash slow and very dim. if the hazard lights are turned on, both of the tail lights flash slow and dim, and also out of synch with the front.

when the headlights are ON, the front lights all function, but the blinker functions blink faster than they are supposed to, and also the blinker arrows in the dashboard blink as fast as the outside front lights, and in synch.

when the headlights are OFF, but the amber running lights are ON, the stop lights do not work.... and the running lights seems to flash dimly- and sometimes sporadically, sometimes steady.

i checked fuses that relate to brakes, lights and blinkers- as according to the owners manual- the fuses in the dashboard (that i checked) appear to be good. all of the bulbs are good, and work as they are supposed to, as I noticed from when the headlights are OFF.

I also checked all of the fuses in the power distribution box under the hood, they all appear to be good. I have not checked any of the relays, as none of them are specifically listed as controlling lamp functions

added note #1 : the licence plate light bulb(s): when I noticed they were not working, I replaced the bulbs, and they both worked when the headlights were on. the driver side bulb has blown since I replaced it. note: the bulbs I replaced the old ones with came off of a parts truck and were not brand new. currently, the passenger side bulb is working. I used a circuit tester on the driver side and it says it works. I do not know if these bulbs were working before the tail lights quit working. I mention all this just in case it turns out to be relevant information for the bigger problem at hand.

added note #2 : the back up reverse lights do not work either. the fuse in the dashboard for this appears to be good. the bulbs appear to be good. I do not know whether or not they worked before the tail lights stopped working.

added note #3 : I thought this issue could be related to a bad relay for the turn signals/ flashers. the owners manual makes no mention of this relay existing on the truck... at least not in the power distribution box where it is supposed to be. is there a 2nd PDB the owners manual is not talking about, or is this relay located inside the dashboard somewhere? im sure it MUST have a relay for this function- doesn't make sense for it not to have it. does it have something else that controls it? or is it just called something else?

im sure the stop light switch is good, because when the headlights are off, the stop lights DO come on when the brake pedal is pushed. also the blinkers and hazard lights work when the headlights are turned OFF....in other words- if the headlights are turned off, you wouldn't know there was a problem

what could the issue be? a few days ago, everything worked as it was supposed to. I must admit I am stumped and totally out of ideas.

 

[ncranchero]

Sounds like a classic issue of a bad ground. Is it with the headlights only or does it malfunction when the "parking" lights are on?

Emailed you some info.

 

[iLoveMyExploder]

Sounds like a classic issue of a bad ground. Is it with the headlights only or does it malfunction when the "parking" lights are on?

I just went and checked- when the amber running lights are on, the stop lights do not work.... and the running lights seems to flash dimly- and sporadically

 

[iLoveMyExploder]

SOLVED!!!!

after getting underneath it and taking a good look at the wiring harness connector behind the rear bumper, it was pretty dirty inside and out. I took it apart, and noticed one of the male prongs was burned and black looking, and the female end where that one connected to- was melted a little around the outside. I am no expert, but I guess it must have gotten wet and caused a short inside the connector.

after disconnecting the battery, I cleaned both ends out as good as I could with wire brushes, and used battery anti-corrosion spray many times. as it dripped away, I could see dirt and whatever leaving the connector ends. dried it up with a hair dryer, connected it back like it was supposed to be, reconnected the battery, and now all of the tail light functions work again., including the reverse lights.

the mystery is solved, but the problem most likely will return until both ends of the connector are replaced with new ones, since one of the connections appears to have fried out. after a visit to a couple parts stores, I learned that this particular part has to be bought from the dealership. maybe the old one will hold up for as long as he needs it to.