trailer lites 2025
mferris reply :
how would i go about checking the wiring on the receptacle on my truck with an ohm/voltmeter...sometimes my trailer lites work and sometimes they don't. i had my boat at a dealer last year and he said the trailer wiring was ok...i see they have testers in bps but i can't find any around here....
Jayson reply :
Hey how you doing,
where do you live??? I found mine at walmart. or you could go to any auto parts store like kragens, napa, car quest.
Hope this helps 
H-SCbassman reply :
Like Jayson, I also actually found my tester at Wal-Mart. I was just browsing in the boat section one day and stumbled across one for like $5, and the lights on my trailer had been acting up a little bit, so I figured I would give it a try. Everything checked out ok on the connector on my truck. After playing around with the harness a little bit, I figured out that if the contacts weren't connected just right, some of the trailer lights would not work. Therefore, if everything checks out ok with the tester, then I would suggest connecting the trailer up to your car and wiggling it around a little bit to see if its just a bad connection. Also, try varying how far your trailer connector is plugged in to your cars connector. I have one or two contacts that have a few millimeters exposed, which probably isnt ideal, but it seems to work. Good luck! - Jon
mferris reply :
i didn't see any at walmart,i'll check auto stores tomorrow maybe...i've wiggled the wires around with no luck..changed the plug on the truck last year...no change..theres a rubber block under my truck(nissan frontier)where the wires come out of.i'm just wondering if that is where the problem is...
burleytog reply :
Buy a can of electrical contact cleaner and use it often.
ohio_bassin reply :
Testing with a multimeter is kinda tricky, But you can set it on ohm's and check for breaks in the wires. The tester the others have talked about can be found at Autozone or Advance auto also. Your problem sounds like you are loosing your ground. Check the white wire, it should be attached to the trailer frame. Look for any corrosion there and on your plug.
mferris reply :
thanks,i found a tester...truck seems ok..i guess i'll check bulbs and wires on trailer...
Jayson reply :
cool you found one 
Yeah I had a similar problem, I had to rewire the whole trailer lighting.
Ranger364 reply :
Before you go crazy rewiring the trailer try checking the ground. Some trailers ground through th hitch others ground off of the truck/tow vehicle. 90 % of these types of problems are caused by intermittent grounding. Then I would check the pigtail connection on both the vehicle and trailer. Most trailers have the ground wire attached to the trailer.
Just a suggestion.
mferris reply :
apparantly my waterproof lites aren't waterproof....one lens still had water in it from last year and of course the socket is pretty well corroded...i'll probably buy a new lite....thanks for your help....didn't get to check it today with new bulbs.started raining so maybe i'll try it tomorrow
burleytog reply :
Just buy a set of LED lights and be done with it.
Ghost Rider reply :
is your hitch and your ball rusted up? thats part of the grounding system. wires may look good but they could be shot in side. Make sure your hitch and ball are grounding out and make sure you have a good ground on your trailer comming off your plug.
Ozarkie reply :
Sounds like a grounding problem.
I have several trailers all have a ground wire on the connector, white wire on autos and trucks. The wire should be grounded to the trailer with a screw, remove the screw and clean it up, then make sure the ground goes to the frame of the tow vehicle. These should fix the problems.
I never trust the trailer to ground thru the ball/coupler as you can get the exact problems you posted about.
Plus I pull to the river or lake two/three times per week and grease the coupler and ball.
Same for the three gooseneck trailers I have a dedicaited ground wire may be all you need.
Ozarkie
mferris reply :
i got the directionals and brake lites working but i think the socket is so rusted i couldn't get the running lites to work..i took burley's advice and ordered a set of led's...thanks for the trailer ball tip ghost rider,never heard of that..i've never really had a problem with any of the other boats i've owned so i think it's the socket........ozarkie..what do you do cut the white wire's from the trailer plug and fasten them to the boat.....
burleytog reply :
The white wire coming out of the male plug should be attached to the trailer tongue.
I don't know where you ordered your LED's, but Wal Mart has a great set of tail lights for $49.
If I could afford it, I would switch all of my stuff to LED.
mferris reply :
i ordered them from BPS..they had some on sale for 49.95 plus shipping of course...walmart here didn't have any.just had some regular trailer lites..i don't have any wires attached to trailer tongue..3 whites come out of harness and into tralier plug..maybe its grounded somewhere else on the trailer...anyway i'll get the new lites on and see what happens..thanks for all your advice...
burleytog reply :
New lights won't help if you don't have a good ground.
What type of plug do you have on your trailer? 4 way?
If so, there should be a white (ground), a green (right stop & turn), a brown (running lights), and a yellow (left stop & turn).
I was having a lot of trouble out of my lights last year, so I re-wired this winter. Turns out the ground wire wasn't even attached to the trailer.
mferris reply :
yes a four way..i checked it yesterday and i have 3 wires going into the single terminal on the trailer plug..i assume 1 ground for each(running lite,direction,brake)..then they must ground on the truck..i will look under the trailer tomorrow to see if i can find a ground attached anywhere...
mferris reply :
any new suggestions...i bought a new trailer bar lite,,did just about what everyone has suggested..seems i have no or low voltage on some running lites..directionals and brake lites work..no running lites and when i turn on running lites directionals go out..would the only thing left be a wire problem inside the trailer frame..........desparate for help..i really don't want to pay a dealer $60.00 per hr to fix this........i did install led taillights and rather than ground them directly to the studs as suggested by seasense i used the same ground wire for the old lites..don't thing that would make a difference but who knows....
StatosDadRI reply :
pipe-lights .com did my entire trailer 2- 2" red 2- 2" amber and clear tails All LED for under $60.00 including the grommets and new pigtails. Lights are optronic's top quality
burleytog reply :
Quoteyes a four way..i checked it yesterday and i have 3 wires going into the single terminal on the trailer plug..i assume 1 ground for each(running lite,direction,brake)..then they must ground on the truck..i will look under the trailer tomorrow to see if i can find a ground attached anywhere...
Should be 4 wires going into that plug.
The symptoms you describe sound like a classic ground problem.
You can buy a wiring harness & wires from any place that carries trailer accessories (Tractor Supply, Northern Tools) and have it rewired in about two hours. Less if you use the quick clips rather than solder on the connections.
http://www.accessconnect.com/trailer_wiring_diagram.htm
Ground those tail lights to the studs ASAP!
mferris reply :
i messed up typing..it is a 4 wire plug..i found the ground attached inside the tongue....but what i found was there are3 grounds going into the plug terminal and 2 browns going into that terminal on the plug..plus green and yellow so i assume there are 2 circuits for the taillight(brown) and 2 circuits for the ground..also noticed my lite bar was wired different then the picture..mine had a ground on it (white and brown)..all my wires go through the trailer..(nitro).......
burleytog reply :
Can't really get a handle on what you're saying.
3 grounds?
There should be two wires running down each side of the trailer. A brown and the corresponding color for the brake/signal lights.
The brown will be spliced at the side marker lights (if you have them).
The white wire coming from the trailer plug should be (and sounds as though it is) screwed into the tongue.
Any way to take photos?
mferris reply :
don't know if the picture is gonna come out but i think i'm gonna end up bringing it somewhere..i don't really want to run the wires exposed under the trailer and i'd probably screw it up anyway...i don't need the tail lites for another month or so cause it will be too cold in the morning anyway....if the picture did comeout that white blob is 3 white wires,i believe one goes to trailer for ground,one to taillites and one for brake/directionals..also has 2 browns..must be one for taillites and one for brake/directionals....thanks for trying to help.....
burleytog reply :
Is that a factory wiring job? :-?
mferris reply :
yes it is..before i do anything else what difference does it make if i grounds new led tail lites using ground from old lites or grounding directly to the studs..do led's draw more power or affect other lighting..
burleytog reply :
The ground coming off the lights is there for a reason.
On my trailer, the ground coming from the plug is grounded to the tongue. The side markers are grounded to the mounting screws. The tail lights are grounded to the mounting studs. All lights are LED.
Is the frame on your trailer a channel or tube?
mferris reply :
i guess i could try that..do you have a lite bar on the bottom of the back of your trailer also?..maybe i'll talk to the dealer to see if i could ground everything to the tralier like yours..i don't want to make matters worse and i'm a bit frustrated so it's best if i don't work on it for awhile!!!!!!..i guess the frame would be tubular,the wires are completely enclosed with no access except small holes where they come out of the trailer.....
burleytog reply :
No, my trailer is less than 80" across, center light isn't required.
Tube frame will make for a tougher re-wire job.
Ghost Rider reply :
Does any one still make a tube trailer any more?
As you see in the thread 99% of light problems are ground issues. A wire brush and some elbow grease will go along way. oh if you have splices in the wires it is a good place to check for problems. If you find any repair and replace. Use a heat shrink over any connections that you can. oh check the wires before repair if you see green past an 1 inch go ahead a re- wire the trailer. i am not sure about your state but if dont have to have side marker lights dont use them.
mferris reply :
i've replaced all splices..grounds are clean..all lites have resistence with ohm meter...i think i surrender...i moved the ground on my truck..the only weird thing i found today was that although i bought a tester to plug into my truck and it shows everything is working ok when i have the directional on i'm getting low voltage in all the terminals on the plug on my truck yet if i turn just the headlites on and have 12 volts coming out of truck plug i only have something like 2 volts going to the first set of side lites..and if i check continuity with an ohm meter from that first set of lites to the trailer plug i get continuity so since i have very little hair to begin with and have been pulling it out for 3 days..i give up....once again thanks for all your help.....
Ghost Rider reply :
did you check the hitch and ball for rust? Shake the trailer on the ball and see if that helps.
Dont use the ohm meter it will just jack with you. Did the truck come with factory tow package? or was it an add on? Well what year is the truck there oould be two problems you are having. I will pm my phone number to you call if you want the help.
rboat reply :
I had a problem very similar. I was reading low voltage at the lights. It turned out to be the little black box in the tow vehicle. It is a transformer of sorts with diodes in it to protect your trucks electrical system. A worn wire or little spark can fry that box. Make sure you have good wiring on the trailer and then replace the box. I just cut the wires and spliced in the new black box. Works great and the box was only $25.
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