New light kit problem

[lefty2]

Hi,

I just installed a new light kit on a small trailer. I have a 4 prong connector. There are two tail lights, each has 2 bulbs. There are also two marker lights, one on each side. I have the wiring correct based on diagram and research on the interwebs. I have the white ground going to the trailer frame.

Here's my problem.

Marker running lights work fine.
Blinkers work fine.
Break lights work fine.

However, the rear running lights do not come on. But when I remove the large light bulb, the two filament bulb, the smaller bulb in the tail light comes on. As soon as I stick the big bulb back in, the little light goes out. The big bulb, the two filament bulb, never comes on except when breaks or blinker are on.

Quick note: when I remove the big bulb in the tail light and the little light comes on, it's not super bright. Although, this is my first light job so I guess that's relative to what my experience is with bulbs in general. I've also tried multiple big, two filament bulbs in the socket. I've also tried more than one fixture in the tail light position with the same results.

I though it might be a bad ground so I thoroughly cleaned the tail light mounts and ground wire mount. My truck is very well maintained and I keep the plug socket clean. I'm at a loss.

Thanks in advance.

 

[smokeonthewater]

Re: New light kit problem

You have a ground problem
EDIT: OR multiple ground problems

 

[Mi duckdown]

Re: New light kit problem

What kind of Truck or VEH? A test light will help a lot. I'm A little confused myself with your problem.

 

[Alan Lloys]

Re: New light kit problem

+1 on a ground problem. It can really do weird things on the lights.
Are the rear lights the standard ones that mount with 2 bolts through holes in the trailer? If so try and clean off a small area down to bare metal where the nuts contact the trailer. I have had issues before where the holes are a little big and the light will not ground properly as the bolts are not making good contact in the over sized holes.

Alternatively try and take a piece of wire and touch it to a known, good ground on the trailer and then to the bolts on the rear lights. See if the lights come on then.

 

[lefty2]

Re: New light kit problem

What kind of Truck or VEH? A test light will help a lot. I'm A little confused myself with your problem.

I have a 2008 F350. I tested the vehicle with a voltage meter and was getting 12V out of the running prong.

 

[lefty2]

Re: New light kit problem

Are the rear lights the standard ones that mount with 2 bolts through holes in the trailer? If so try and clean off a small area down to bare metal where the nuts contact the trailer.

Thanks Alan, Yes, they are standard with 2 bolts. I used a grinder to get past the paint where the nuts make contact with the mounting bracket.

I'm going to try your suggestion with a piece of wire.

I was thinking that since the problem is bilateral and has been replicated with the old fixtures as well, that it might be the ground from the trailer to the truck, which I just installed new. But I have that main ground pretty well situated. I drilled through the frame of the trailer and used a sheet metal screw to connect the ground to the trailer from the truck. I gave that area a good rogering from the grinder as well before installing.

If it is helpful information, I'll also add that I tested the running light contact in the light fixture and was seeing 12v as well. I'm not sure what a fault would do to that reading if it existed because I'm not an electronics guy.

Thanks

 

[UncleWillie]

Re: New light kit problem

When it absolutely makes no sense at all and it appears that Magic is at play.... It is a Grounding Problem!

The Big Two Filament Bulb is the Brake, Turn, and Tail light,
The Smaller bulb is likely a side marker.

The Brighter Filament in the Double Bulb is the Brake and Turn Signals combined. Powered through the Green/Right and Yellow/Left wires.
The Dimmer Filament is the Tail Light. Powered through the Brown/Marker wire.

If it isn't a ground issue, The BROWN wire to the rear lights has a problem.

 

[smokeonthewater]

Re: New light kit problem

It COULD be a ground issue in the middle of the trailer too..... Depending on how the trailer is built.... A set of jumper cables can help you Check that....

 

[lefty2]

Re: New light kit problem

Thanks to everyone for the suggestions, which were very helpful. To solve the problem, I ended up wiring the market lights on a parallel circuit. I noticed that when I bypassed the markers, the tail lights worked perfectly.

I think the marker light bulb, a small bulb, was providing too much resistance. The weird part is the instructions clearly stated to pass the power through the marker.

What I ended up doing is spicing off the brown power for the market and then grounding the marker. This solved all the problems and now they work correctly....or do they? They seem to.

 

[smokeonthewater]

Re: New light kit problem

Ahhhh that would do it... You originally had it wired in a series circuit and NOW it's parrallel.... It is correct now... Could never work in a series circuit.

 

[lefty2]

Re: New light kit problem

I thank you. If it wasn't for a 2nd grade science fair project many years ago, I would never of thought of it. I distinctly remember saying to my classmate..."like we're ever going to need this again".

 

[BigDfromTN]

Re: New light kit problem

I thank you. If it wasn't for a 2nd grade science fair project many years ago, I would never of thought of it. I distinctly remember saying to my classmate..."like we're ever going to need this again".

Like me in high school Typing Class!!!!

Glad you got it fixed!