Tail/clearance light wiring question

[Not-a-tent]

I have a 1985 T-1661. The left and right turn/brake lights work. The left tail light works. But the right tail light does not work and none of the clearance lights work.

I traced (what I believe are) the tail/clearance/turn/brake light wires to the left rear corner of the trailer to where they disappear under the shower pan. I'm assuming they penetrate the wall there, but can't see that they do.

Where do the tail light/clearance wires go from there? My guess is that they go to the left tail light and fan out from there to the right tail light and clearance lights.

I have a good ground at the right tail light. But I don't have any continuity between the left tail light and the right tail light. I am therefore assuming there is a broken power connection at or near the left tail light that feeds the right tail light and the clearance lights. Any idea of where that connection is and how to access it?

Dave

[EMD_Driver]

I am not sure how they wired the 85 models, but the 2004 model we had was wired like this: The feed from the front of the trailer came down the street side. Wires for the right tail/stop were run across and up to the light assembly. Marker light supply wires were run up the left-rear corner and across the back. You can see that the wires came from the left(trailer's left), in this picture..

[Not-a-tent]

From your photo, it looks like the splices/connections were made at the lights. Was that true of all the splices/connections? Were there any splices/connections (e.g., several wires crimped together) inside the walls some distance away from the lights?

Looks like the next step is to remove the tail lights and see what wires I can access.

[EMD_Driver]

If memory serves, they were all daisy-chained....

[Steve Collins]

In my '99, all the wiring was continuous runs from one fixture to the next. All the connections were at the pigtails for the various lights, and were done with wire nuts that were then dabbed with silicone caulk.

I did some rewiring in '10 and '11, and all the connections were OK, but darkened with oxidation. If lights are not working, checking these connections after verifying that bulbs and sockets are good may find the problem.

The front marker lights were wired separately from the rears on my '99. The wiring went from the end of the 7-way pigtail on the floor straight up the front and daisy-chained from the street side low marker up and over the front and down to the curb side marker.

Bad ground is a major cause of problems with trailer lighting in general. Start with the bulb and work backward checking to see if you have solved the problem as you complete each step:

• Test the bulb first! Or swap out the bulb for a known good one.
• Clean all contacts and coat lightly with dielectric grease.
• In the tail and marker light fixtures, make double sure that all contacts are contacting properly.
• Then pull the fixture and check the pigtail connections to the trailer wiring. If they are suspect, remove the wire nuts, undo the wires, sand them lightly to brighten contact points. Coat with dielectric grease and reassemble using new wire nuts, preferably those that have threaded metal inserts in them. When tight, apply a dab of silicone to keep moisture out.
• Find the ground points. There should be one or more under the trailer, generally along the street side. They usually use standard grounding lugs screwed to the frame, similar to this:
• 
• Grounding points are subject to corrosion and vibration. They are inexpensive and readily available in the electric aisle of any hardware store or big box home improvement store. If it looks bad, it probably is. Replace using a new screw. Sand the frame where the lug will go, first. Make sure the exposed wire that is going into the lug is bright and shiny (sandpaper is great for this) and then coat all wiring and the lug and frame point with dielectric grease. Tighten everything securely.

[mainah]

I was missing only a few clearance lights and it turned out to be a poor connection at the ground point at the converter buss bar where all the grounds on mine go including the interior lighting.

[Not-a-tent]

Thanks for the info. I think I now have a pretty good idea of the wiring layout. Shouldn't be too difficult to find and fix the problem (famous last words ).

Dave

[Not-a-tent]

Just a brief update in case others may find it helpful.

I recently purchased a 1985 T-1661. It had not been used much during the past several years and time and the elements have taken their toll. The left tail light was working but the right tail light was not and none of the side marker or clearance lights were working.

I now have both tail lights, both rear side marker lights, and two of the rear clearance lights working. The main problem was that the "hot" wires to and the contacts on the lights had become heavily oxidized, preventing the wires from conducting electricity along the daisy-chain from one light to the next.

The left tail light is the first light in the circuit. It was getting power so it worked. But the oxidation on the wire from the left tail light prevented any electricity from flowing to the next light downstream (the left rear side marker light). And oxidation on the wires and contacts of the left rear side marker light prevented electricity from flowing to the next light downstream (the right tail light). And so on.

So I have been proceeding one light at a time -- disconnecting the "hot" wires from the light, cleaning the exposed ends of the wires and the contacts, reassembling, then checking. So far I've done the right tail light, the two rear side marker lights, and two of the rear clearance lights. I stopped there because I was getting cold (the trailer is outside and it was only about 30*F) but anticipate I'll be able to get the rest of the marker and clearance lights working eventually.