I have a 99 automatic and a brand new 15x5 SLM Enclosed trailer. The brake lights and turn signals work but the trailer has a bunch of LEDs and other running lights on it and they don't light up. They won't light up on my buddies 2000 24 valve dually either. Only the brake lights and turn signals work. So I'm curious if any of you guys have ran into this before. It's a 4 way flat and I'm using an adapter to plug up to the stock plug that comes on our trucks. I tried to call SLM but they are closed until Tuesday. I wanted to try to figure out what's going on this weekend. Any ideas?

Does anything on trailer lite up when you turn your head lites on?

Put +12V power to the brown lead and ground the White lead. The trailer running lights should work. If so the circuit on the trailer is good. Now check the socket where the brown wire would be on the truck. There is a Trailer Relay in the PDC and there should be a fuse also for it as well. Make sure the trailer fuse and the relay are functional.

Let me just make the observation...  bulbs will light in either direction...  LEDs have to be polarized correctly.  Trailers typically have a lot of non-standard wiring.  Colors can be anything etc.  

 

I just put side lights in my enclosed trailer.  I tested polarity when I installed LED tail lights & ran the side lights off the tail lights on each side.   

 

 

I am like Mr Squire above. They wont light with out the head lights on.

Sorry I didn't think of this sooner.

Brake lights & turn signals ARE the separate parallel sides of the same circuits.  Brake lights will come on without any other power...  they will in your truck too.  Truck running lights (markers, tail lights) power up with parking lights or head lights positions. 

So you tried on 2 trucks.  The trailer is NEW.  I wonder if the adaptor you are using isn't connecting the correct leads.  It's too late for me to dig in the shop for the pin out of the 7 blade RV connector tonight (after midnight).  I had a lot of trouble with cheap china trailer connectors that would not properly seat in my truck OEM trailer connector.  The one I bought at NAPa works fine.

   

The ones I had trouble with...  looking at the trailer side of the connector...  the chromed contacts extend side to side beyond the opening...  I think they'er made on metric machines & my truck wouldn't mate with it.  I found this after I wired it all up! 

My previoius thread on this:  http://forum.mopar1973man.com/index.php?/topic/7538-new-rv-7-pin-plug/

Edited September 6, 20159 yr by flagmanruss