Simple flat 4 trailer wiring, 10 minute job right?
I bought new (non LED) lights and a spool of wire, the wire is color coded but also has its destination stamped every 8". Plug it into the truck, nothing. OK, ground the test light, poke one of the two pins inside the socket; light. Flashers on, I get blinkies. Put the bulb in - Nadda.
I tried 7 different bulbs! What's going on?
Did you ground the wiring on the trailer?
Might have voltage but high resistance somewhere. Check the light directly from the truck (maybe short jumpers from the connector) to see if the fault is internal to the trailer wires or not.
But also I agree, make sure the lights are grounded
Trailer wiring is so frustrating.
What type of bulbs? 1157 or 3157? 1157s are notoriously difficult. Not the bulbs themselves, but the bases. It takes very little corrosion or dirt to make them completely ineffective. Add to that, many manufacturers make them so wimpy that they just never work right.
If you can't tell by looking at the filaments, do a resistance check across both contacts to the collar to verify that the bulb is bad.
A bad ground is usually the culprit. Causes strange over-amping. When I do a ground on a trailer, I run the wire to a self-tapper screw with a toothed lock washer between the ring terminal and the frame. The teeth on the washer dig right in and make sure it grounds. Same goes for the ground wire near the tongue. On the truck, I went a little overkill. I did a 3/8" stainless bolt, drilled and tapped the frame, and did the same toothed washer trick.
If your lamp housings use the studs to ground, be redundant and add a wire to the frame. Often times in an effort to not rip the studs right out of the housing, people don't tighten them enough to get a good ground.
Ifi it is acting weird, its a ground issue.
Ground the trailer to the truck with a set of jumper cables and mesure from frame to frame just to be sure. Then go looking for bad grounds on the light fixtures.
Had you bought a trailer wire harness I would not ask, but how cheesy is this wire you are using to wire the trailer? China makes some pretty lousy wire that they sell cheap.
For trailer wiring I run a ground wire all the way to the lights just to make sure there are no ground issues. Too may times I have been bit by bad grounds.
zordak said:For trailer wiring I run a ground wire all the way to the lights just to make sure there are no ground issues. Too may times I have been bit by bad grounds.
YEP , did you check for power at the trailer light sockets ?
I am also going to add a clearance light for each side on the trailer fenders so I can see them out of the rear view mirror to make sure the running lights are still hooked up......
Got it - got it! Ran some errands this morning and the first thing I did was plug the trailer to the truck and ran a jumper wire from my known good ground to the light. LIGHTS!
Everything looks good so why assume the metal light bracket welded to the frame is not grounded.
Rule number one about trailer wiring. It's almost always the ground.
Lights too dim? Ground.
Lights too bright? Ground.
Lights doing weird psycho flashing? Ground.
Right blinker flashing when left blinker is on. Still probably the ground.
Toyman01 (Moderately Supportive Dude) said:Rule number one about trailer wiring. It's almost always the ground.
Lights too dim? Ground.
Lights too bright? Ground.
Lights doing weird psycho flashing? Ground.
Right blinker flashing when left blinker is on. Still probably the ground.
It's ALWAYS a bad ground. That's electric diagnostics 101. I had a license plate light and reverse light (only time that light EVER worked) that would blink on left signal. The signal light did nothing, but those other lights would blink. Right signal was fine. Turns out it was a bad ground. Lesson learned.
This is exactly why I never ground a trailer through the hitch. I also always run a ground wire through the trailer harness & to all trailer lights.
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