Trailer Tail Lights Not Working

Frank Chyz

Seaman Apprentice
Joined
May 16, 2015
Messages
37
Brake lights and turn signals work fine but tail lights do not come on. Same problem with a box trailer I pull from time to time. What should I be looking for on the truck side of things?
 

dpoff

Petty Officer 2nd Class
Joined
Nov 27, 2004
Messages
169
I guess get a test light or volmeter and test the connection on the truck, should be the brown wire, then go from there.
 

sublauxation

Lieutenant
Joined
Oct 13, 2008
Messages
1,317
You can get a 4 prong tester for a couple $ or as mentioned, just use a volt meter or test light. I've had to replace more than a couple truck end plugs in the past years.
 

Cat nip

Petty Officer 1st Class
Joined
Jul 25, 2015
Messages
288
If its a Chevy it mite have trailer light fuses in the under hood fuse block .
 

NYBo

Admiral
Joined
Oct 23, 2008
Messages
7,107
If its a Chevy it mite have trailer light fuses in the under hood fuse block .

Good call. Actually, many (most?) trucks have separate fuses for the trailering harness. My '07 Dodge Ram does.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
The brown wire in a trailer harness is the tail lights. No power at the plug, check the fuse. If the fuse is ok, then the wiring is buggered.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
The brown wire is the tail/running lights and runs from the trailer connector to a point where it splits and runs down both sides of the trailer. Think of that wire as a pipe with water running through it. Follow the juice with a voltmeter or test light. When you lose the power you found the problem./
 

Ironic

Cadet
Joined
Apr 18, 2016
Messages
6
I've run across the same problem with my trailers. In my case, I kept blowing the fuse in the fuse box under the truck's hood. Your truck's owner's manual will tell you which fuses are for your trailer lights.

I later found that I had a bad ground in my truck's trailer plug recepticle. I changed the "outlet" and haven't had any problems since.
 

Whatever1969

Recruit
Joined
Sep 29, 2014
Messages
2
This season mine weren't working either. I ended up chasing the wiring and discovered that mice had eaten the insulation off of them. They were shorting against each other and the trailer rail.
 
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