ok i have a 99 dodge 3.9l dakota sport 4x4 an i was driving around an someone let me know i didnt have any taillight so i pull over to check it out an nothing so i mess around with them an replace bulbs an brake light switch, after messing with them for over 3 hours i finaly get the right side to work normal but the left side the blinker blinks really fast an if i hit the breaks with running lights on the break light an running light getts really dim an the reverse light comes on... any ideas plz help...

 

you, my friend, have the classic short.

The blinkers are resistance-to-ground based. The higher the resistance to ground, the slower they blink. The less resistance (see: short), the faster they blink.

Looks like your break lamp wire and reverse lamp wire got crossed/shorted. In reverse, do the running lamp/brake lights come on?

Here's something to help you sort it out:

 

ok now i was out their messing with them an nothing again...

 

the blinking fast is usually caused by a bad ground, trace the wires and look for bad connections

 

ok whats the quickest wat to find a short,, i do have a voltmeter, an test light

 

bad ground? I thought it was short to ground? Or is it short to power? Because LED's cause the flashers to stay on, from lack of filament resistance.

Stupid electrical systems.

if your voltmeter does resistance, quickest way it to use it as a 2 probe test light- test each bulb-socket contact to ground, then to another socket.

My manual is an 00-04, so doesnt include your 99. But electrical wise, it shouldn't be much different. My first suspect would be the 7-way trailer plug, if yours has one (i doubt). 4 pin doesn't have reverse, so it wouldn't do it.

The rear tail lamps are dual fillament- one fillament is brake/marker (black/yellow), one is turn (the other one, could be any combination of green, red, and brown).

So you hit brakes with markers on, and reverse illuminates. Well, brake and marker is the same wire, and are double-energized.

Reverse is violet/black, and goes directly to the transmission. When in reverse, the transmission completes the circuit (supplies power). The brake/marker and turn signals are powered by the CTM. The only common point, is the ground (the whole housing grounds together, i think). That said, I would find that said ground, then cross-check all 5 pins on each side of the truck for continuity. Only the 2 grounding pins should have continuity, the other 3 should have nothing.

Best way to do this- hold one probe on reverse pin 1, and probe the 3 brake pins- 1, 2, 3. then do the other reverse pin, and go 1-2-3. same with other side.

 

Personally, Id just check your trouble areas underneath. It will be easier with your spare tire out of the way. Those black looms contain all of your rear lighting. notice how vulnerable they can be at the tail lights to debris from your tires? Look for worn and/or chipped insulation or bare wires. Some electrical tape whether the liquid kind or not should do the trick.

You can use the voltmeter and put the probes on the wires in question. Then have a partner go and wiggle wires underneath and you are looking for fluctuations in readings (that are not as a result of your hands not holding the probes steady). This will help you narrow down where the short is. Beware: you may go through a few fuses with the latter method lol.

 

if fuses haven't blown yet, not sure they woiuld during troubleshooting...but never hurts to have a few spare onhand anyways.

 

ok when i replaced all the bulbs headlight taillights blinkers,, all of them the all called for the same 3157 bulbs ,,, an it had the trailer thing were it had plugs that pulg into each side of the tail light wiring harness,, but i removed it an it still didnt fix anything,, ok i will get out their with test light an volt meter an find out were my short is i guess,, an yes it has resitance test on it ,, i have a feeling im going to see alot of the underside of my truck for the next couple of days

 

I have one of the aftermarket trailer harnesses, can almost guarantee that it won't have anything to do with those, built tough. But I added the 7 pin to mine, and the contacts are all pretty close together, thats why I said a 7 pin would short easily if put together wrong.