SD F150

I got an 2007 F-150 XLT. The yellow "running lamp?" burned out on my trailer. I replaced them, and they do not work. I tested the wire, and no electricity is going to it. I looked up the fuse, and am guessing it is in the manual as:

R201 Trailer PARK LAMPS Half ISO RELAY

Obviously, I got to go to the dealer for this one. Has anyone had this fuse/plug blow? Or anyone have a trailer know if this is the correct fuse for that yellow light on a trailer?

Thanks!

Mod (Ret.)

A fuse blows for only one reason: overload on the circuit. For example, if the fuse is rated for 15 amps, then it blows when something on the fuses circuit draws more than 15 amps.

A relay is used to allow higher amperage circuits to operate on a "small wire" switched trigger; a small 12 volt "switched" circuit (light switch, on/off switch, etc) will provide 12 volts/low amp to a relay. The relay will have a heavier guage, higher amp lead to the relay, as relays can handle up to 30 to 40 amps. When the "switched" circuit is on, the relay passes the heavier amp circuit to the output circuit. Relays can be easily trouble shooted by listening for their "click" you hear when the relay "clicks on or off" based on the switch being operated (on/off switch, etc). This saves the switch itself (headlight switch, simple on/off switch, etc) from burning up, as the small copper contacts inside this switch would pit or burn up from the high amperage.

So, you'll need to literally trace that yellow wire from it's source to it's destination (destination being the trailer plug?) and source being the fuse box/panel. I'll suspect a short, meaning this yellow wire is touching a ground somewhere in it's "path", or the relay is bad. Check the relay first; most are located in the fuse panel, located on the passenger side, lower kick panel. If the relay is found to be good, then check for any "previous owner" splices around the area of this wire or trailer plug first. Ford does a great job of insulating the wires and connectors; it's very rare for any of them to short out. It's usually going to be a bad splice or cut from a previous owner.

Whatever you do, DON'T PUT A HIGHER RATED FUSE IN ANY CIRCUIT TO KEEP A FUSE FROM BLOWING!. This can cause the wire itself to heatup, and burn, causing a fire. You don't want that.

I mention this only because I've heard and seen folks do this.

SD F150

Thanks for the advice. I am the original owner. I am going to FORD today to check the relay. I dont think it is the wiring, it is pretty clean on the trailer.

Thunderslide

I am a little confused. where do you have power to? anwhere? did you find a blown fuse?

SD F150

I have a boat trailer, and the yellow running/parking lights burned out on each side. I hooked up new lights, but they didnt work. So, I assumed, the fuse was blown. When I went to the FORD manual, it didn't show a fuse assigned to these lights (unlike all other lights on the trailer, they have a assigned fuses). It showed there was a relay assigned, not a fuse, as shown below.

R201 Trailer PARK LAMPS Half ISO RELAY

Thunderslide

so you don't know if you have power at the rear of the truck? you just know there is no power atthe lights? Do the tail/brake lights work with the lights on or do the yellow ones just not work. I think that the tail lights and yellow lights are on the same circuit. are you using the 4 pin or 7 pin plug? If the red lights come on with the lights (not brake lights) I would check the trailer wiring for a broken wire.

SD F150

There is power at the rear of the truck, the RED tail/brake, turn, lights work on the trailer. It is just the Yellow lights that do not work.

It is a 4 pin. I guess I should check the connections.

Mod (Ret.)

So, you're talking about the yellow side marker lights on your trailer???

If so, there's nothing wrong with your truck, seeing as how the red taillights on the trailer are working. Save yourself a trip to the dealership, as the truck is fine. Check the wiring of the trailer!!!!

Trace the yellow marker lights wiring to the 4 plug trailer harness that plugs into the truck.

If it is the yellow side marker lights you're refering to, then they should connect to the same lead as the trailers red taillights.

Thunderslide

I am sorry if my questions annoyed you I was trying to help you diagnose the problem. The problem with trying to help is I don't know how much you know about anything. From your description I didn't know what you tried. Somewhere along the line I thought you had changed the lights not just the bulbs. how would I know you "hooked" them up right? my first inclination would be to see if the connection to the truck was working.
clearly that was not yours. If the tail lights are working the marker light should be as well. If the tail lights are working the problem is in your trailer not your truck. Go ahead and run your truck to the dealer and let them charge you to test it.

When asking for help be polite about the help you get.

They make testers that are cheap http://www.dual-star.com/index2/Tool...t%20Tester.htm

SD F150

I was rude?

You didn't annoy me, I was just trying to be clear on what light was working by typing RED!

Thanks for all the advice, so yes, it is the yellow marker lights on the trailer.