On my 02 Dakota I noticed it has a middle connector on tail light wiring that has harness on end 4 wire..
On left side the Brown an green an right side the yellow an blue-GROUND..
I'm trying to test it to see that when lights an brakes are on with blinker that it's functioning correctly.
Checking with test light for the light circuit are ok an blinker ok an separately with lights off brake circuit on..using test light..i can't tell when lights are on during braking if there any change in bulb..

​​​​​When I use meter on blinker circuit with brake an lights on the reading fluctuates all over from 10 to 3 to 7 to 11 in any sequences.Is this normal reading?

How do I know or test that it's its operating correctly w lights on an brakes an blinker since 1 circuit has blinker brakes combo on it .?

When I try to connect to trailer it works fine but if lights are on ,an I brake,it all goes out till I let up on brake.
How can I tell if the problem is on wiring coming from Truck an how can I test it ?


Any info is appreciat​​​​​ed.

 

Sounds like you have brake and running lights crossed I think. Are you running off of a flat-5 or round 7? (J560 is outdated and not used anymore)

 

On truck at lights there is a middle connector that goes to trailer connectoin,between tail light connections on both sides.2 wire middle connector for each side.

After that I have a 4 wire connector -has Brown an yellow off left ,,an green an purple (purple is GROUND end on harness ) off right..

How can I TEST that I'm getting correct reading off this connector for brake light /blinker both at same time ..and with lights on too?

 

I don't understand what you mean? I'm not following at all. Is it an OEM round 7? Violet is supposed to be backup lights...

 

The same wire for brake lights sends signal for blinker ..how do you test that they are working correctly when both in use ..braking with blinker on ......an head lights already on.

It's the older​​​​​​ type end to trailer. 4 wire..an other side is harness behind wire tail light connection.looks like factory

 

Test light is the only way you can really test it (with a known good ground at that). When you were saying brake, I was thinking trailer brakes feeding the brake lights (I've seen some newer trailers wired that way).

Other option might be that you are using single filament bulbs in a dual filament fixture or vice-versa on the trailer.

Typically in the lack of a formal ground, the other lighting circuits become a ground- tails ground through turn/brake, turn/brake ground through tail. If turn/brake and tail both have 12V, the light goes out until the formal ground is returned.

 

Im using the 1157 2 filament bulbs..

Only way to test it on truck I guess is to try a working trailer that's good with everything on..blinker , lights ,,brake..together.

It's wired pretty simple on trailer- 4 wires Brown for lights split to both sides an yellow an green for blinker /brake an white -ground.

.Does length of Ground wire on trailer .. from trailer connector to metal factor in ?

Ground wire on harness ,bolted to trailer metal ,is about 4 ft from connector ,i also have another GROUND in back from both tail lights to frame.
And is it a must that the trailer be actually fully on the hitch of truck vs plugged in but not touching Truck ( for more grounding)?
Thanks

 

I figured out the truck wiring is fine..
Took it to Home depot an tested it on their trailer..wire connect only
What do I need to try with the rewire on trailer ?
Look for GROUND issue?