LED running lights

Seems to me I have the 1157 base. Can't check right now. Trailer is in MD. I am in Bermuda so it will have to wait a few weeks.

INFAMOUS SCANDAL OVER 3157 LED STOPLAMP BULB!

Vendors listed in writing the bulbs are a direct replacement for standard incandescent 3157 bulbs that function BOTH for a tail and stop/turn lamps.

THEY LIE their ass off in writing to customer direct inquiries about the bulbs compatibility.

So beware before buying. When Detroit decided to abandon 1157 and 1156 bulb bases they opened the door to this fustercluck world of "It fits upside down".

This warning comes from the world of reality, not conjecture. It applies to 1156 1157 duty 3156 and 3157 bulbs.

Years ago the FTC and DOT would have issued warnings. Now they issue politically correct propaganda.

What bulbs are you using, I think that there was a problem with using some of the bulbs like the 921 as the can be installed two ways. One is backwards electronically, pulled out and rotated 180 degrees and reinstalled and they work.

I know I had that problem with my recessed lights in the entryway to the S&B.

I've got to order some of those for spares.

Polarity eh? OK, will try that. The object of the exercise is to get somewhat brighter lights. Common red lenses that are sort of dark. Situation made worse when coated with road dirt. Always trying to upgrade this & that. This was supposed to be a dead easy job till Murphy showed up to help.

Polarity!
I would test the LED units. Use a set of light wires a couple feet long. Connect one end to a battery power source, touch the negative to the shell of lights and tap the positive side to center contact. Lights should work. If not reverse the leads, if they now work, then your system is reversed in trailer.
If they do not work, return them.

I would return them, get a refund, and roll with the incandescents before I would start breaking loose caulk and butyl tape to gain access to the pigtails, for reversing the leads.

I see little benefit to LED for running lights unless one is worried about how much power is being used while traveling, or are one of the clowns that needs to have them lit up all night in the campground.

LEDs are polarity sensitive, incandescent bulbs are not. Try swapping the leads to the nonfunctioning LEDs.

Beyond that, it's standard electrical troubleshooting. Do the lights work when you test them in isolation with a 12V power source? Is power getting through the wires to them? Is your trailer connector solidly connected to the tow vehicle? and so on.