Turn signal

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Rideandrepair, Nov 26, 2022.

  1. Rideandrepair

    Rideandrepair Road Train Member

    14,964
    49,691
    Aug 8, 2015
    0
    Been having this problem for a while. My right turn signal indicator light will illuminate very weak, and fade on and off. Only happens when the headlights are on, and only when my Trailers hooked up, (plugged in). It has always went away before, now it’s constant. No right turn signal at all with lights on, and Trailer plugged in. Also no 4 ways. Only the full time indicator. Turn lights off, everything works normal. Unplug Trailer, everything on Truck works normal, with lights on or off. I took the switch apart, stretched the springs out, checked the points, greased it up. Good as new. Problem still exists. Using a test light, I checked the pigtail and 7 pin receptacle on Trailer. Everything’s working right. Checked the plug for right side Tail lights on the Trailer. All good. Thought maybe the light itself was shorted out. Swapped another tail lamp, still the same. It’s as if the right side running light wire on the Trailer is shorting out the turn signal wire, since it only does it when headlights or running lights are on. Similar problems with right turn signal have always been fixed by rebuilding the switch. Sometimes simply by unplugging it and plugging it back in. A mechanic suggested that on my last Truck. Said he doesn’t know why, but they’ve found it works. It did. Had to do that a couple times on my last 99 Classic. This ones a 2000. I originally figured it was in the Trailer, since it only does it when plugged in, but it checks out. Test light shows the same results at the tail light plug, with or without the lights on. I’m at a loss.
     

    Attached Files:

    Last edited: Nov 26, 2022
  2. Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.

  3. 062

    062 Road Train Member

    5,522
    21,115
    Oct 20, 2013
    0
    Does it have separate relays for right and left?
     
    Rideandrepair Thanks this.
  4. Rideandrepair

    Rideandrepair Road Train Member

    14,964
    49,691
    Aug 8, 2015
    0
    I’m not sure. I think so. I did some more guessing. Now when I turn the right signal on, all 4 rear trailer lights come on Lol. I think it’s in the 7 pin receptacle on the trailer. The pig tail checks out. With or without lights on. But when it’s plugged in, with lights on, and right turn signal on, all 4 trailer lights blink, and everything on the receptacle lights up except brakes. It’s the type with circuit breakers. I’ll get a new one tomorrow. Nothing’s available today. Hopefully won’t get shut down for it. Turn signals are required lighting.
     
    Siinman Thanks this.
  5. 062

    062 Road Train Member

    5,522
    21,115
    Oct 20, 2013
    0
    Your op sounds like a weak relay/breaker, but the last post sounds like a bad ground. I have seen a tail light that had so much corrosion on the plug it caused all the lights to flash.
     
  6. ducnut

    ducnut Heavy Load Member

    924
    2,449
    Dec 31, 2010
    Paradise
    0
    Bad ground, is my guess. As mentioned, the plugs are very susceptible to corrosion and that’s almost always been my problem. However, I had the running light filament in a bulb break, lay across the turn signal posts inside that bulb, and caused wacky behavior in all my turn signal and running lights, exactly like what you are describing. Check all the incandescent bulbs, on your tractor.

    Also, Lowe’s sells a product called Ox-Gard, in their electrical department. That stuff is what you want to use on any non-sealed connectors, like the plugs on your trailer lights.

    https://www.lowes.com/pd/Gardner-Bender-1-oz-Ox-Gard-Anti-Oxidant-Compound/4514334

    B824911C-4550-48C9-8D8A-610E789374F2.jpeg
     
  7. kwswan

    kwswan Road Train Member

    1,687
    8,385
    Jul 26, 2009
    mcminnville,tn.
    0
    Try unplugging the trailer tail lights and plugging them back in 1 at a time to see if the problem shows up.
     
    loudtom and lester Thank this.
  8. BoxCarKidd

    BoxCarKidd Road Train Member

    3,925
    5,570
    Aug 26, 2014
    0
    I find the post a little hard to follow so lets clear it up some for me please.
    1: Everything works when the trailer is not connected? If so most likely a trailer problem.
    2: With the trailer connected, head - running lights on, all four tail lights flash with the right turn signal on? If the marker lights do not flash at the same time I suspect the four tail lights are on a common ground together and it is bad.
     
  9. loudtom

    loudtom Road Train Member

    1,451
    2,247
    Aug 26, 2016
    0
    I've had a bad ground on the left trailer turn signal that would make all the markers on the left side blink as well. Another idea about your light being dim is that the turn signal and marker wires have been reversed for that light, so the markers will be bright and the signal will be dim.
     
  10. Raffito

    Raffito Light Load Member

    81
    51
    Aug 25, 2019
    Conroe
    0
    Have to agree with everyone that says it’s a bad ground. Start by fixing all trailer ground wires and 7-way ground. Depends on the age of the trailer, would be good to run separate group for turn signals and lights.
     
  11. BoxCarKidd

    BoxCarKidd Road Train Member

    3,925
    5,570
    Aug 26, 2014
    0
    More likely a bad ground on that one turn signal bulb. A strand of wire out of place in a multiple pin connector can cause havoc.
     
  • Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.

  • Draft saved Draft deleted