Trailer wiring mystery

[Gary Dotson]

I'm confused! I bought a 2015 Silverado, with factory towing package and installed my brake controller. The factory supplied pigtail was still in the glove box, unused. Anyway, when I finished, I got out my handy, dandy LED tester and plugged it in. Nothing, no 12v., no lights and no brakes. Using a test light, grounded to the bumper, I had power everywhere it was supposed to be. At this point, I'm assuming a ground issue with the connector so I removed it for examination. The ground was good so I looked for a connection issue and found none. I can probe, with the test light, inside the connector, using the ground pin, and everything tests normal. The only issue is that this silly little plug in tester, that works perfectly on both of my other vehicles, doesn't work at all on this one. When the ground firms up, I'll connect to my trailer, I'm pretty sure everything will work right. While it's not a big deal, this thing is bugging the heck out of me, anybody got a clue?

[Jim Becker]

I can only think of one thing. LEDs are polarity specific and test lights aren't.

[muleboss]

Maybe the bumper has a poor ground, not making good connection.

[Barnyard]

Maybe the bumper has a poor ground, not making good connection.

Using a test light, grounded to the bumper, I had power everywhere it was supposed to be.

[Dale Finch]

Curious, was the trailer actually hitched to the truck?

[tst]

some newer vehicles the function is computer controlled, and may have to have it activated by the dealer

[Barnyard]

Curious, was the trailer actually hitched to the truck?

When the ground firms up, I'll connect to my trailer, I'm pretty sure everything will work right.

[Gary Dotson]

I considered the polarity issue and checked it, no difference there. The bumper is well grounded (just like the owner) It got firm enough, this afternoon, to drive out back and check, with the trailer connected (but not hooked up, just plugged in the pigtail) As I suspected, everything works perfectly (except that stupid little tester). I'm hoping more people have some thoughts, on this because it makes no sense to me. I don't have a problem, it works just fine but I do have a mystery. All thoughts are welcome.

[Don McCombs]

I have always thought that electricity was magic.

[Jim Becker]

Have you verified that the LED tester works on one of your other vehicles after it didn't on this one? I'm grasping at straws here.

[dgrapes59]

Gary, being the electrical wizard you are, I can understand you wanting to solve the mystery. But, some things you just need to accept they work, kinda like a thermos..... Keeps the hot things hot and the cold things cold, how does it know??

[muleboss]

Maybe the bumper has a poor ground, not making good connection.

Using a test light, grounded to the bumper, I had power everywhere it was supposed to be.

You got me on that one. Better learn to read better.

[Barnyard]

Maybe the bumper has a poor ground, not making good connection.

Using a test light, grounded to the bumper, I had power everywhere it was supposed to be.

You got me on that one. Better learn to read better.

I miss that stuff myself quite often.

[John *.?-!.* cub owner]

On my truck the harness a lead with a ring lug that has t5o be bolted to ground. I have also seen some of those pigtail that the ground does not pss through.

[Gary Dotson]

Checked all that, John, I even put on a new connector on the off chance that I was losing ground through the connector. As I said earlier, the trailer lights and brakes work fine, just not the tester. Yes, Jim, I tried it again on both the Traverse and motorhome, works fine on either. Yes, David, I understand that some things in life remain a mystery, but I'm having a hard time letting go of this one. It just seems too obvious, it should work. Maybe, my newly acquired pick up has some sort of top secret, proto type electricity. That makes about as much sense as anything else I've come up with.