Hello all, so I post this as I have come to the end of my rope dealing with a trailer light problem. A bit of background first, I run a Curt T connector kit on my toyota pickup for my trailer lights. Have had it working flawlessly for the past year. All of a sudden, after a unfortunate trip down a logging road with my boat and trailer I noticed a problem. When I put my turn signals on, either one, both trailer lights flash. Running lights and brake lights work fine. When I don't have the running lights on the turn signals worked properly sometimes, other times they dont come on at all. So assuming it was a trailer wiring problem I tore into the trailer lights and wiring and 9 hours later no progress. So to isolate whether it was the truck or trailer causing the problem I plugged my trailer into a friends vehicle with the same flat 4 connector and all the trailer lights worked properly, not a problem with anything. So the problem has to be on the truck end. So thinking that my curt convertor had gone I got a new one, and after installing it there was no difference. I checked my ground coming from the connector and it was fine, solid connection. I tested the plug coming off the convertor with a circuit tester and everything checked out, was getting a signal on both turn signals and from the running lights, as soon as i plug it in to the trailer I loose either the running light circuit or the turn signal. I have an led connector on the trailer end plug and not once did the turn signal led flash when the running lights were on, the led for the running lights would be slightly flashing and therefore both trailer lights would flash. So I tore into the wiring on the back of the truck, going over every bit of exposed wiring, cleaning up anything that looked not right and removing any old wiring from the PO for trailer wiring. 8 hours later and same problem, gone over all the exposed wiring at the back of the truck and found nothing. Asides from pulling the entire wiring harness off the frame I have no idea what to do next. Another note, all the truck lights are working no problem, turn signals, brake lights, running lights all fine. I cant believe how frustrating this is especially since I never had a problem until all of a sudden. Any ideas would be greatly appreciated as I have zero idea on where to go from here, Thanks.
Trailer Wiring Mess
- Thread starter vanisland
- Start date
scott craven
Well-Known Member
I would be tempted to plug your truck connector in to a buddies trailer and give it a try, if all works fine
you will know the problem is somewhere on your trailer, most likely a poor ground.
If the problem is on your truck, try U Haul as they have helped me before.
you will know the problem is somewhere on your trailer, most likely a poor ground.
If the problem is on your truck, try U Haul as they have helped me before.
spring fever
Well-Known Member
RS craven is right-poor or bad ground somewhere and x2 on the buddies trailer.
Whole in the Water
Well-Known Member
I have given up on having lights on the trailer itself.... repeatedly putting electrical connections into saltwater is just a problem waiting to happen IMHO.
I now have my light mounted on a 8ft 2x4 that hangs off the back of my boat. They always work and never get into the water.
I now have my light mounted on a 8ft 2x4 that hangs off the back of my boat. They always work and never get into the water.
Da Bay Bye
Active Member
Given all the information that you have provided, I would suspect the trailer ground is the problem. An easy way to check is to run a wire from the ground on the truck. Ensure it is grounded to the truck, activate the light you want then go to the back of the trailer and touch the ground wire to the bolts that hold your light on the trailer. If you get the correct light with this, the ground on the trailer is the issue.
I have found that most light issues are ground problems with trailers.
Hope this helps
I have found that most light issues are ground problems with trailers.
Hope this helps
Thanks for all the suggestions so far guys, so I plugged my truck into another good trailer and as I suspected I got the same result, so the problem lies in the truck. I've gone over ever inch of exposed wiring and found no frayed wires or anything. And I have tried grounding the wiring harness on the truck end to different known good grounds and didn't change anything. This is a puzzler, I'm out of ideas so I'll go see the guys at uhaul like RS suggested. Any other ideas anyone has? Thanks again
fshnfnatic
Well-Known Member
Thanks for the info,Phil my boat.Although I'm a very mechanically inclined person,I always have trouble with electrical
stuff. Can't tell you how many times I've pulled my hair out over a trailer wiring issue.
First post!
Been lurking for the last month. Disabled and not much to do. i thought I"d take up fishing hence here I am.
I registered reading this morning. just could not help to pipe in. All guys got it all wrong.
You need a new a new module. Let me know how it goes?
How do I set up my profile?
Hookin'up
Well-Known Member
check the grounds on the yota tail lamp assy's particularily where the ground screws go into the plastic housings
also pay real close attention to the bulbs, I have seen brake lamp filaments break off and drop down and short to the running lamp filament
bulb still works but feeds into the other circuit at the same time, look real close at the filaments
I worked for toyota for 15+ years and this was a major issue brake and tail circuits
also pay real close attention to the bulbs, I have seen brake lamp filaments break off and drop down and short to the running lamp filament
bulb still works but feeds into the other circuit at the same time, look real close at the filaments
I worked for toyota for 15+ years and this was a major issue brake and tail circuits
Just to explain it to all about this problem since I am bored. Toyota has a separate bulbs for brake & turn signal. The trailer uses same bulb for brake, signal & running light. Brake & turn use the same filament on the bulb. Running light is separate. What the module does is the brain to let the trailer lights know what you want to do. Before the trailer the signal going to the back is all separated. But it is all joined in the trailer harness. Follow so far? Without the module, everything flashes, both sides. The module separates all that & also stops feeding back to the vehicles wiring system. That is it folks.
Hookin'up
Well-Known Member
Perhaps we should ask what year the toyota is, previous years use a combination brake/turn bulb and not separate as you suggest
Lol
You are the the Toyota guy. Just ask away. Or see if he has amber at the back. Then it does not matter what year, make or model.
Thanks everyone for chiming in. Hopsing when you say module, are you talking about the convertor box that comes with the t connector harness? If you are I have replaced it with a brand new convertor kit and same result. I have separate amber rear turn signals and red running lights. Truck is a 93 T100 with the plug and play harness for that specific model.
