When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Every trailer that I pull has no running lights. Been this way since I got the truck which was over 6 years ago. I do a lot of trailering, but most of it is during the daytime. The brake and turn signals work just fine. But the running lights do not.
Does anyone have a clue how to fix this, or where to start looking? I went through the fuses and they are all good.
Which connection are you using? The factory 4 way or factory 7 way connector?
The 4 way has ground, left, right, tails (park). So if you're using the 4 prong, are you saying your tail lights aren't working while you have the park lights lit up? Or with the headlamp in the off position? You can also buy those testers that plug into the 4 way connector. http://www.uhaul.com/MovingSupplies/...Tester?id=4821 is one for example.
If you're basing this on a past truck you had (not that you have - but wondering if this is the case), they may have wired the tail lights to ignition making them operate at any time when the key is on, rather than when it's technically supposed to be (park light position). Especially if it wasn't factory installed.
We need a bit more detail unfortunately. If you're turning your park lights on during the day and it's not lighting up, then I'd be checking if you have power to your connector for tail lights. If you're leaving your headlamp switch in the off position and expecting lights (on a 4-way connector) to be on, they won't be. If on a 7-way, it can be done but the trailer needs to be configured that way. I often turn my headlamp switch to Park to illuminate mine. The only other way you can do it is use a 7-way, wire to the battery and wire to battery. I don't believe battery is switched though so if you shut your truck off your lights would stay illuminated.
The most helpful would be (for a start): Which connector you're using? Is it factory? And what position is your headlamp switch in when you're expecting the running lights to illuminate?
There is a fuse for trailer running lights. It's also tied into the truck's reverse lights. I'd check that fuse double to be sure. Thats what happened when my trailer running lights quit
I had the same problem. I pull a trailer - but mostly after hours - so I need tail lights.
Checked everything from fuses etc - nothing - everything was good. Finally got frustrated and started tracing the harness back....
So the issue was the plug that went into the 4-pin / 7-pin....the wire that was feeding the running light portion was so corroted that when I pulled the tape / insulation back - it was just dust.
So I ran a new wire and fixed I have tail lights.
AGAIN, my issue was between the plug and the 4pin/7pin in the bumper.
I'm using the 4 way connector. The running lights on the trailer aren't working. On a trailer, you have brake lights, running lights, and turn lights. Brake lights work when I hit the brake with the headlights on or off. The turn lights work with the hedlights on or off. The running lights don't work when the headlights are on (no need for running lights when headlights aren't on).
I've got through the manual and pulled every fuse that said anything about trailering. Maybe I'm not pulling the right one? Does anyone know the right one?
I can't imagine having an issue like this for 6 years and not resolving it.
The basics of a 4 wire connection are quite simple.
Green is right turn.
Yellow is left turn.
White is ground.
BROWN is tail lights and running lights.
The brake lights come on from the green and yellow. Given that your problem exists across multiple trailers, you can rule out the trailers and your problem is that your BROWN wire has no juice. Check it with a meter. If no juice, inspect the wiring to see if it's broken. You could also check the same wire on the 7 wire plug if you have one.
According to your manual, fuse 10 (page 239) is for trailer backup lamps relay and trailer tow parking lamps relay. Check it.
That tester looks pretty handy, I'll be picking one up. I hook up to quite a few different trailers pretty often, and of course the lights tend to not work. Usually from mice or brittle wires and loose grounds. This tester would be nice to have on hand to rule out the truck each time.
One other thing I found with quite a few f150s, is I think the left directional not working on trailers. There is a fuse in the top right of the fuse box, that is usually blown that causes this. From what I remember, it's not listed as anything as far as trailer lights in the manual neither.
12-12-2014, 08:50 AM
Running Lights (Trailer)
- but wondering if this is the case), they may have wired the tail lights to ignition making them operate at any time when the key is on, rather than when it's technically supposed to be (park light position). Especially if it wasn't factory installed.
