Tail light fuse problem?

[Witch Doctor]

Originally Posted by KyDan

Get a meter and start your truck and measure between 1 oclock and 7 oclock on your 7 pin RV socket on your back bumper.
1 oclock is the 12+ and 7 oclock is ground.
IF you have 12-13 volts there you already have the relay and fuse installed.
I say to start the truck because some trucks don't supply power to the
socket unless the engine is running.
My Chevy has power at the socket 24/7.
Here's a graphic to show pin outs on the socket.

Good Luck!

Dan not to highjack this thread but I looked at your picture. My running lights keep blowing a fuse 15 amp. I had to replace it with a resettable one being no one can find a short. The diagrams shows tail and running lights at the same pin, but my tail lights still work when my running lights blow. You have any idea why?

[KyDan]

This isn't going to be easy but maybe someone will have an idea-
I think we need more info from you.
When you blow the -running lights fuse- do you mean a fuse in your
truck??
AND do your truck running lights go out or the trailer running lights go out?

I don't see how it would be possible for the TRAILER to have tail lights and not clearance lights since these are all fed from one pin in the socket.

There might well be 2 fuses in your truck- 1 for side markers and 1 for tail lights but there is only 1 wire going to the trailer for both tail lights and clearance lights.
The truck separates these with isolation diodes I guess but I'm way out
of my experience here.
Hopefully others will have some ideas.

[Witch Doctor]

Originally Posted by KyDan

This isn't going to be easy but maybe someone will have an idea-
I think we need more info from you.
When you blow the -running lights fuse- do you mean a fuse in your
truck??
AND do your truck running lights go out or the trailer running lights go out?

I don't see how it would be possible for the TRAILER to have tail lights and not clearance lights since these are all fed from one pin in the socket.

There might well be 2 fuses in your truck- 1 for side markers and 1 for tail lights but there is only 1 wire going to the trailer for both tail lights and clearance lights.
The truck separates these with isolation diodes I guess but I'm way out
of my experience here.
Hopefully others will have some ideas.

My Ford Truck has a seperate fuse for the running lights only for the trailer, about every 50 miles or so they will shut off. My break and tail lights still work, all truck lights still work. I have taken it into Ford they said I do not have a short in my truck or connector. I have taken to the dealer, they checked it and said they can not find a short and it would be impossible to try and pull new wire to each running light. They said that they checked each running light and can not find anything. So I put a resettable fuse in it's place. It is a 15 amp fuse in the truck. the lights pull about 2 amps when on. I can jumper out my TT plug and they will stay on until I disconnect it. Do you think I might have a staple going through a wire and after bouncing down the road it will short? In order to reset the fuse I have to turn my lights off and on again. Then everything works again. FR just threw there hands up in the air, Ford say's it's not my truck. The dealer even hooked it up to there truck and drove it around but they didn't blow because they only went around the block. In a lot of states it Illegal to drive without your lights on in the rain. If you need any more info please ask. When a state say's your lights have to be on during rain would that include the trailer running lights besides your head lights?

[Flybob]

I think the confusion here is between running lights and side marker lights. See attached bargman connector. The tail and running lights are on the same pin on the connector. If the fuse for it blows you will have no running or tail lights, BUIT you can still have side marker lights as they can be on a separate pin.. If it is the side marker lights that are shorting, it is very possible that a screw has pierced a wire and as the trailer is moving, it allows the screw to touch the wire. This can be very difficult to locate. If this is a new problem, check any recently installed screws.

[Witch Doctor]

Originally Posted by Flybob

I think the confusion here is between running lights and side marker lights. See attached bargman connector. The tail and running lights are on the same pin on the connector. If the fuse for it blows you will have no running or tail lights, BUIT you can still have side marker lights as they can be on a separate pin.. If it is the side marker lights that are shorting, it is very possible that a screw has pierced a wire and as the trailer is moving, it allows the screw to touch the wire. This can be very difficult to locate. If this is a new problem, check any recently installed screws.

They are the little clearance lights I guess you call them. No this is not a new problem, I have had it since the 5er was new and been living with it. Just do not know what else to do. Do you know Flybob if they are required on during the rain? I really never drive at night anymore so I don't worry about that. It just bugs me when something is not correct on my unit...I guess it would be the clearance markers, red and yellow about 2 x 4" there are 4 across the back top , 2 in front and a few on the sides. Thanks for clearing up my terminology. I pulled the junction box where my plug go's to and tightened all connections and then taped them off. Do not know what else I can do.

[Flybob]

I am not sure about the need for clearance markers during rain, it may be state dependent. Certainly sounds like a wire being nicked or damaged and as several people have said not easy to locate. You may contact your dealer, but it is possible that correcting/locating it may result in other more serious issues as the wiring is pulled through the walls/roof very early in the assembly process. I suggest the resettable breaker available at most auto parts stores.

[Witch Doctor]

Originally Posted by Flybob

I am not sure about the need for clearance markers during rain, it may be state dependent. Certainly sounds like a wire being nicked or damaged and as several people have said not easy to locate. You may contact your dealer, but it is possible that correcting/locating it may result in other more serious issues as the wiring is pulled through the walls/roof very early in the assembly process. I suggest the resettable breaker available at most auto parts stores.

Thanks I also think it is a staple touching a wire when I hit a rough spot in the road and it shorts out. I have installed the resettable fuse already, Thanks for your help.....