Riddle me this...

[tantrum]

This doesn't seem to be causing any problems, but i find it odd.  I have my new trailer hooked up to the truck.  The trailer has LEDs.  I recently added LED bulbs to the truck.  When I put the truck in "drive" the trailer lights turn on.  I put the truck in park, neutral, second or low, the trailer lights stay off. 

[lesman01]

sounds like the wire harness is hooked up wrong. What happens in reverse? Can you back up or does the trailer surge brake engage. FWIW, when in reverse, the surge brake is disengaged so you can back up.

[tantrum]

The wiring harness plugs into the factory plug on the truck. I can back up fine, no surging.  The only other thing I have had happen when I put the LEDs in the truck is the radio and clock light would dim as if the headlights were on.  This was without the trailer connected and now that doesn't happen.  It's pretty funky that both of these only have happened on drive.

[HCollado]

You actually have a choice... shoot the truck or the trailer.


However, since the trailer in new, I would shoot the truck. One of the two is possessed.

 

On a serious note, it sounds like the relay switch on the truck can't handle it. My two cents.

[cyclone]

What kind of LEDs did you put in/on the truck? You could test what's going on with the trailer by using a meter and two jumper wires for power and ground to the trailer connector. I'd turn on the lights, see how much current it pulls, then add up each fixture to see if the current draw matches the load. Is this a factory trailer?

[wakejunky]

Very strange some of the old Toyota converter boxes would heat up and actually melt. you might check that, but it sounds like something is tapped into the gear selector switch. maybe two harnesses shorted together. what happens if you put the old factory taillights on? LED's do very strange things to electronics. eliminate the truck or try the trailer on another truck.

[eagle1wi]

sounds funky for sure - I have one of these testing connectors - you might want to see if you are losing the connection in other gears all the time (for example when just this little tester is on there) or just when the trailer is pulling current - they make these both as a singe tester and a pass through as well - so you can leave the trailer connected - see pics

worth its price to isolate whether it is the truck's problem or the trailer

[tantrum]

The LEDs came from superbrightLEDs.com, not sure of the name brand.  The trailer is not a factory trailer, it is an EZ-Loader.  I am thinking it might be the LEDs, so pulling those out and then hooking up may be the easiest place to start.  At first after the LED install sometimes the radio and clock light would dim as if the lights were on too, that has seemed to go away, guess the gremlin got bored.  That tester looks like a good idea just in general, might just have to get one for future sanity!!!  I just don't understand how lights would tie into gear selection other than reverse.