Stefanieb

So I have a (brand new) horse trailer and everything works just fine on it, except for the interior lights for the inside of the stalls and the dressing/tack room. The dealer mentioned my F150 (which is an '05 5.4L 4WD just as an FYI!) is probably just missing either an auxiliary or battery charger fuse and that's why the light isn't working.

Anyone have any experience like this and could you tell me where to locate either of these fuses to check them out? THANKS in advance!

RGSMDNR

theres a fuse and a relay to install... check the manual.

Abn150

Look in your fuse box under the dash on the passenger side. There should be a space for a relay and a fuse labeled "trailer tow battery charge". In the 2005 models, the relay is position R05 and the fuse is position 106, 30 Amp.

If both of these are present and working, then you have other problems, check if they are there and then report back!

If you have break-away brakes, which is likely on a horse trailer, this is more than just an interior light problem, it is also a safety problem, since this is the same circuit that charges the battery that powers the break-away brakes.

Stefanieb

Ok I will check this weekend, thanks for letting me know! I do have breakaway brakes, but I tested them by pulling the pin out when I first got the trailer and they worked. How would a fuse in my truck be attached to those? Just making sure I'm not missing something! As they are set up now, there's just a cable that attaches to my truck and if the trailer was to detach from the truck, the cable would pull out the pin and the breaks would engage on the trailer. So theoretically the power cord would detach first, then this cable that releases the pin, so there would be no power to the trailer anymore anyhow, right? Maybe what you're calling breakaway brakes are something else, different from what I have though, not sure! Definitely something I want to look into though, I'm of course always worried about safety when trailering my equine girl!!

Thanks for the info on the placement of the fuses, now I know where to start my search! I'm going to go ahead and expose myself as less of a truck guru than the rest of you though and ask what a relay is? I'm familiar with replacing a fuse, done that before, but never messed with anything else electronically on this or any other truck before!

Stefanieb

Oh and I just re-read your statement "that charges the battery" and realized I'm a moron LOL! I get it now, so more than likely when I first got the brand new trailer the battery for the brakes was already charged up and that's why it worked fine...but NOW, who knows, battery could be dead!! NOT good!

Abn150

You are absolutely correct on how the break-away brakes work, but there is one more step - since in a break-away situatoin there would be no more power to the trailer anymore, there needs to be a power source IN the trailer to engage the trailer brakes. That is the break-away battery.

The location and type of battery depends on your trailer make. On my Equi-Spirit/Hawk, it is located in a box against the wall in the tack room. On some trailers, it is actually in a box outside on the trailer tongue. Once you find it, if you have access to a voltmeter or battery test light, you can see if it is still charged.

It is possible that your trailer uses a non-rechargeable battery. If this is the case, you still need to test it periodically and then replace it when it gets weak.

Abn150

A relay is basically an electrical switch that is controlled by another switch. It allows a lower current circuit to control a higher current circuit. According to your owners manual, the trailer battery charge circuit needs a full ISO relay. Your dealer or local auto parts store should be able to help.

benchwarmer4203

Replacing or adding that relay will be the same concept as replacing a fuse...it just looks different. It's the bigger piece of equipment in the fuse block that looks like a little black box. I'm not sure if it'll have 3 or 4 pins, haven't looked at this particular relay in a while. It serves a different electrical function than a fuse, but is physically replaced the same way...you just plug it in.

Stefanieb

Thanks so much for all of your help! And yeah my brake battery is in my tack room as well, and of course right after I posted that initial response I figured out what you were talking about haha...batteries do need something to charge them lol! DUH.

Stefanieb

Ok so the dealership looked at it and said that relay and fuse do exist already in my truck and look to be working fine..so no idea why the lights aren't working now! Anyone have any other ideas??