Turning on the running lights through the trailer plug

[Keith_Smith]

Yes, I know this has been a topic that has received a lot of flames, and I'm not asking to be able to use this while camping. I was just playing around with the fiver tonight in my driveway (just finished packing bearings today), and was wondering if I could make the running lights come on using a jumper across the plug. Just a curiosity.

I tried jumping across the hot lead on the fiver plug to the one that turns on the running lights and it doesn't make them come on. I put the end of my test light into the hot lead of the plug and grounded it against one of the bolts on the hitch and the red light of the test pen comes on. If I reverse it and put the alligator clip of the test light into the hot lead of the plug, and then put the pointed end of the test light against one of the bolts on the hitch, the test pen has a green light turn on.

Anyone play with this and have an idea of how this is working? Like I said, not something I intend to use. More just trying to understand my electrical system.

Wondering too, if I can make the brakes turn on and off while sitting in the drive this way.

[Keith_Smith]

I think I figured it out finally. I had a bad ground wire. Battery was good. I ran a new ground to the frame and everything seems to work the way it should. I'm not sure how far back the original ground wire ran or where it was supposed to tie in. I assume it goes back to the inverter box (or whatever that is actually called). I'll dig into it further when it cools down here. Thanks for everyone's suggestions.

[time2roll]

Yes it works. Should be pin 3 & 4. Use a 12v automotive flasher if want them to blink.

Used to be a product called Flashcube that you would just plug onto your cord. Had two switches... On or Flashing.

[opnspaces]

Maybe your jumper wire wasn't long enough to make contact inside the plug.
It sounds like from your post that you had the ground hooked up so it should work when connected as you described.

[icechip]

I used to just run a wire from the positive post on the battery to the run light in the trailer wiring plug.

[grampachet]

If you are using a 12 volt test light it will light up but not provide enough resistance to light the rv lights.

[bob213]

We have used the flasher method when we had an emergency. Sherriff told us it made it much easier to find the TT in need of help with the flashing lights in a dark campground. I always carry a flasher with me now. I have the correct plugs marked so even the DW could find the correct position if she had to.

[rwjejits]

Is your trailer 12v batter wired up and disconnect (if you have one) turned to the "on" position?

[robsouth]

Is your camper battery good? It will only work with a good camper battery.

[Keith_Smith]

Old-Biscuit wrote:
On the trailer plug........

Jumper wire (or automotive flasher) goes between pins at 1 o'clock and 11 o'clock positions.
Looking at end of plug..... notch up
11 O'clock is hot from trailer battery
1 O'clock is running lights

Yeah, I tried that. I'll try using my jump box for power and see what that does. I'll probably blow all my lights by playing around. 🙂

[Old-Biscuit]

On the trailer plug........

Jumper wire (or automotive flasher) goes between pins at 1 o'clock and 11 o'clock positions.
Looking at end of plug..... notch up
11 O'clock is hot from trailer battery
1 O'clock is running lights

[BFL13]

Try more pins. The trailer end is the mirror image of the truck end.

[Keith_Smith]

I wasn't clear on my post. I did run a jumper wire across the hot post of the plug to the running light post. The running lights did not come on.

[Fastfreddy1964]

Try running light pin positive and neg ground from the right of of plug pin 1 and 3 good luck

[way2roll]

Not sure if you are aware but this post is 10 years old.