I have a 2007 Trail-et horse trailer. The trailer has 4 top clearance lights plus a set of three on the top back. On the bottom it has two on the front ether side, one on the front sand back of the fenders and two on ether rear corner. I included a picture like it in case you fall asleep reading my description.
What it's doing is when the lights go on, the top roof lights will go on. A few seconds later the rest will come on. If I shut them off and put back on, they all go on at once. I'll leave it sit over night and the scenario repeats. A couple of weeks ago it started blowing my fuse on my truck, 06 SD with tow package. They would go on and then blow the fuse. My truck was ok because I hooked up to a few other trailers with no problems. The other day I changed my trailer plug. The old one had some play in it. I also removed the lights, sanded down the grounds, changed the screws that held in the grounds to the sheet metal. Plus sprayed down the light connections and truck plug with contact cleaner. I also used dielectric grease and coated over the grounds. Now the top lights will come on then a few seconds later the rest will come on but no more blown fuses.

The question is, what would cause the delay? It seems the current hits a block or something and then works it way past it.

Another question is, does the electrical current remain in the line after I shut it off to a point the block won't occur when I put them back on but after a long period like overnight dissipate and get blocked again?

The real kicker is I know of 2 other trailers same year and model and they do the same thing

 

Electricity should be nearly instant. One possibility it a chaffed or partially broken wire and 'welds' itself together from the draw of the other lights. Blowing the fuse could be the same wire hitting the trailer (ground).

 

This is an interesting question. First a general comment. Occasionally I work on horse trailers and dump trailers and often find their wiring to be "unique". As I am sure you realize, cleaning contacts and using dieletric paste, in theory, should have done nothing to reduce the problem of a blown fuse. The lights may well be brigher, but a short is a short and it takes a short to blow a fuse.

You also know the answer to your own question. Current is not stored in a lights or wires, unless you add something to the circuit. I also can not come up with any reason why a manufacturer would add anything to briefly reduce current draw as trailer lights just are not that much of a draw. I am not of the opinion the wires are welding themselves together, although I understand the thought behind that hypothesis. My own guess would be moisture in poor connections that, once heated, is temporarily reduced or removed, until current draw ceases and then mositure condenses on the connection as it cools overnight.

So how do you test to determine the cause? Good question and a bit of PITA, but you could try wiring the lights yourself to a new wire and power it up. I bet they call come on at the same time. If they do, you can conclude it is a wiring problem, but if the lights are working, do you really want to go through all of that?

Steve

 

Thanks for the replies. What I'm trying to find with this is the direction of the current after it leaves the junction box in the dressing room. The wiring is well hidden through out the frame. It's always the top go right on then then bottom. I can take out the brake lights and see a decent amount splicing and a chaffed wire that was probably caused by yanking it through the frame. I'm guessing it was wired on a Friday an hour before quitting time. I'll be changing the that wire but had temporarily wrap some electrical tape of the area. Hard spot for a quick change.

The suggestion it hits a spot that had moisture or even the other one, a chaffed wire is very plausible. The lower lights do see quite a bit of moisture especially in the winter where it's subjected to snow here in the N.E.

One thing it did do that was weird. After I did the whole ground cleaning and grease thing, I took it it out for a 10 mile ride to see if I had a loose wire that would cause them to flicker or blow a fuse. I rolled about 2 feet. The bottom went off and on quickly. After that it was fine. I hit every bump I could find. Good thing the horses were not in it.

Since I had the lights apart I figured to clean the grounds and throw some grease on them. I know it won't stop blowing fuses but chock it up to over do maintenance.

As I said I know of two other trailers that do this exact problem but not up to the blowing fuses phase which hopefully is over with. The owners are both waiting for me find the problem first.

 

Not sure about the feasibility, but the rule of thumb in the RV world is it is almost always faster to run a new wire than to try to repair an old.

Steve

 

Just to let you know everything works fine. Went through every light, clean every connection. Found some that seem to never completely dry from ether washing or rain. Sealed those. Went through the wiring that I could see and replaced some that the insulation worn off from ripping it thru the frame from the factory.

Now on to my camper with the brakes that don't want to work....

 

Glad to hear it. Brakes are much easier to trace.

Steve

 

That lasted a day. It's back to the delay. About 10-15 seconds for the bottoms and top clearance bar to come on and they do it together. No moisture as it hasn't rained it a week nor has it been on the road. I replaced any suspect wiring that the factory opened the insulation while building. I went through every scotch lok connector to see if one was not connecting completely. I know the Scotchs can cut the wire strands while being installed causing a bad connection. Learned that on my bike. Used them for installing a TFI controller on my bike's ECM. Like jetting carbs on a fuel injected motor. They cut a few wires causing a bad connection and a lousy running motor. Once again after they come on, they will work fine even after several hours of being off. I don't know. I'm leaning towards the welding theory after all this although I've never countered such a thing. Just trying to find the defective connector that goes from the main power to where it splits between the two circuits. That's buried somewhere. I'm also leaning towards a factory screw up because I have a boarder at my barn with the exact trailer and year that does the same thing. I hate electrical.

 

I am still doubtful anything is getting welded as that would not be a reversible process and does not occur even with dead shorts. I don't know what type of light you have, but how does the bulb bracket or socket look. I have no doubt it is a factory screw up. Every time I have to work on something electrical from a low volume manufacturer who does not work much with electrical, the system is always over-engineered and installed in a manner that makes troubleshooting Hell.

NASCAR is here in Bristol this week so I have been doing little other than electrical all week with the campers at the track.

Steve

 

Are they LED or HID lights? Maybe a ballast or starter (or whatever the converter thing is called) is bad.

 

It's a bad intermitted connection somewhere. They have been working fine after I ripped everything apart and checked every Scotch Lok and re did some. Never really found anything odd other then a ground that goes into the hub. When i do the bearing soon I'll see that. Another ground in the wheel well. When I disconnect it, everthing stills works.

I hit a decent bump the other day and the bottoms gave a quick blink. That was a helpful clue to end this BS.

 

If you have a meter that will measure DC amps, measure the amp load on each wire coming out of your junction box (after all the lights come on). I wonder if the gauge wire the manufacturer used is insufficient for the circuit? Interesting that other trailers of the same year and model are doing the same thing. Do the wires get warm?

 

If you don't have an amp meter, try pulling a couple bulbs out of the circuit that is coming on late, and see if the problem goes away.

 

The problem was a ground or actually one of the grounds. There is one attached to the siding behind the rear tire. It's a good spot if you want it to be exposed to the elements. I took it off and cleaned the area of paint plus cut back the wire and installed a new connector. I covered it up with liquid electrical tape. I'm guessing the delayed lights are on this ground. I don't know. The other ground goes into one of the hubs. The lights would work without the ground ( one fixed ) but as said they would be delayed. I went over to the other trailer with the same problem and the ground was not even connected. I showed the owner and he did the repair. His works now.

I just had another trailer come in tonight, same make model/year. No delay but when you hit the brakes, all the lights go on. When you use the left directional all the lights blink. The right side is good. The woman who boards here and owns the trailer never realized it too.