turn signal/brake light issue.

Chevycummins

Chevycummins

Bad case of Tinkeritis!
Joined
Jul 15, 2008
Messages
3,488
i have searched and read several of the other threads about this issue and cant seem to find the same issue that i am having with my truck. i have an 01 and while towing a trailer the other day i completely lost brake lights and turn signals. i turned on my turn signal to make a turn and it blinked like normal and then all the sudden quit and would not do anything. thought it might be a fuse but i checked all the ones inside the drivers side and under the hood and all are good along with the lights.

the others i have seen have either stayed on solid or blinked at a different rate, as to where i dont have anything. like i said i have checked fuses and lights just not sure if the relay will just quit and not work at all or if it should stay on solid like said before with other issues or if there is something else i am missing.
 
Did you lose turn signals on the front of the truck, too? Are there any other trailer plugs wired in other than the factory plug? If somebody did a hack job installing another plug, there could be corrosion and that can cause all kinds of goofy things to happen.
 
i have the front marker lights but no turn signals on front or back and none of my brake lights work. the trailer plug was just put in and was wired and checked 2 weeks ago and installed with heat shrink connectors. had to upgrade from the 6 pin to the new 7 pin RV style like the new ones since everyone has trailers with those connectors now. all worked fine before and my first guess was a fuse and when i looked at the relay it looks fairly new and sure its probably been replaced a time or two in the previous 220k miles
 
Is this the first time you've towed with the truck after the plug was put in? I'd be double checking everything related to that and making sure the grounds are good.

Also, have you tried your hazards (since they're powered from a different source and use a different flasher)? From the sounds of things, I doubt that's going to do anything.
 
no this is approx the 5th or 6th time i have towed this trailer and used a friends enclosed one that uses the 4 pin plug thats built into this plug. havent tried the flashers yet to see if they worked will try that and see what happens. i couldnt even find a specific fuse in either location that was labled for turn signals or brake lights.
 
I just verified fuses and function on my '01...

"Stop Lamp" under hood is a 20A larger size fuse on the left side about in the middle.

"Flasher" for the turn signals is a 10A inside the cab in the upper right hand corner labeled #10.
 
just worded differnent than i expected. long days at work must have just slipped my mind hopefully i can get the a chance tomorrow along with a volt meter and verify it all. i know all the fuses are good for sure thinking about checking voltage to the multifunction switch also.
 
replaced the relay inside the driver side door jam still no luck on getting it to work. any other ideas?
 
yes trailer is unplugged. all grounds at the trailer plug and batteries that i could see are hooked up and not corroded. when i get to work tomorrow i am gonna get my voltmeter that does volts, amps, ohms, and continuity and see if anything is shorted out or that i am getting a current at all
 
Check for voltage, not current. Since you used the flat 4 part of the plug and it worked, then odds are something is messed up on the RV 7 wiring. Just because somebody recently installed it and supposedly checked it, that doesn't necessarily mean it's right. Usually when you go from 4 pins to 7 pins you're adding a constant 12v pin and a pin for trailer brakes (sometimes another aux power). I'm guessing that you probably have a brake controller.. does that change at all when you hit the brake pedal or plug the trailer in?
 
the brake controller appears to function properly when brakes are applied. i havent looked at it after the issue came about to see if its dead also ill check in the am when i head to work. do you happen to have any idea if i should see 12 volts or is there different level of voltage. i have seen some items where they only have like 5 volts or something like that.
 
Brake controllers have an output anywhere from 0-12v depending on how you have it set. More voltage = more stopping power. If its the style with the slide actuater on the front, then you should be able to squeeze that and have voltage to the plug. Some newer ones aren't that simple. The important thing is getting it (and the other functions) to the proper pin(s) on the plug.
 
i actually put the plug in, and when we did it i tested each wire and its function. of course dodge didnt use the same color coordination that everyone else does on normal trailer wiring for turn signals and brakes. we took each individual wire and tested its function and then tested it with the trailer before it was crimped. the trailer is grounded through the ball and through the ground wire in the plug just to make sure there is a good ground.
 
Diesel Powered said:
Why do I feel like I'm not getting the whole story? :kick:

Anyhow, good luck tracking it down tomorrow.
Click to expand...

what do you mean whole story??? :what:

the only thing i have done the the wiring at all was install this plug. when we installed it i took a volt meter and turned on one function at a time to locate the proper wire for the blinkers, brakes and running lights. after each one was located we touched the wires to the plug wires with the trailer hooked up to make sure it was hooked to the proper wire on the trailer lights. each one was checked and tested before it was wired up solid with heat shrink wire connectors.

the whole system worked for the half a dozen times i have towed a trailer since the install and then all the sudden one day it completely quits and i lose brake lights, turn signals, and four ways. no blown fuses and replaced the relay already.
 
That's not a very good way to wire a trailer plug. RV 7 wiring is pretty standard and should follow something like the diagrams in this link...

Trailer Wiring Diagrams | etrailer.com

Double check that with your meter.

Again, it sounded like you only used the flat 4 before you hooked on to the problem trailer.. that's a whole different, less complex, ballgame.

It's odd that a fuse or two didn't blow. There are some fusible link wires, but I don't know of any that would relate to your issues. It's not unheard of to have issues with the PDC. Start tracing with your volt meter and see where you lose it in the process.
 
i know the plug is standard but dodge didnt use the standard wire codes for turn signals, brakes, and park lights. also being up on the farm without internet or a manual thats the way i was taught to track down wires to their functions.
 
Sounds stupid, but unplug your brake controller and then check your function of the lights. Mine decided to stop working on me and it kept the brake lights on constantly until it was unplugged, you might have the opposite problem. Just a thought.
 
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