Headlight relays on a car with concealed headlights

Electrical & Ignition

  1. Kern Dog

    Kern Dog FBBO Gold Member FBBO Gold Member

    Messages:
    20,999
    Likes Received:
    54609
    Joined:
    Apr 13, 2012
    Location:
    Granite Bay CA
    Local Time:
    1:04 PM
    I am trying to understand all of this and am not assigning blame. I simply do not know what is wrong and almost every that step that I make results in one thing: The headlights and doors worked perfectly fine before and now they do not. WHY is the question. Figuring out why is not so simple.
    I unplugged the headlight door wiring and the symptoms continue.
    I unplug the low beam plugs, no change.
    I unplug the high beam plugs, no change.
    I tried different relays, no change.
    When the sensible efforts produce no results, I try shit that makes no sense.
    Ignition on, switch OFF, lights still on, trigger plug pulled out slightly...Yes, there is power to the low beam when the low beams are on and power to the high beam when the high beams are on. Pulling the plug shuts off the headlights as you would expect.

    Something about this kit, no matter how well it was made, upset the system to where it won't work right. It has been consistent today though. Ignition on, headlights on. Ignition off, headlights off. The switch is dead with the ignition switch on but works fine with the ignition off.
    What is it within the system that is disturbed by the relay kit?. I am okay with it being something in the car itself. I'm not looking to blame Crackedback. I may even pull this out to test it in my other Charger. That car has the same style wiring, concealed headlamps and everything. The lights and doors work on the car too.
    I can try the kit on my Power wagon or 67 Dart.
     
  2. 1 Wild R/T

    1 Wild R/T FBBO Gold Member FBBO Gold Member

    Messages:
    3,823
    Likes Received:
    7502
    Joined:
    Jul 9, 2019
    Location:
    California
    Local Time:
    1:04 PM
    The reason the headlights stay off without the relay harness plugged in is exactly why the relays are a good thing.... The relays don't need to see full amps or full voltage to close the relay contacts... Some minor trace signal can fire the relay & the relay takes power directly from the battery & sends it to the headlights... As Rob mentioned probe the leads looking for voltage... With the switch off there shouldn't be any but in order to trigger the relays there must be...
     
  3. Kern Dog

    Kern Dog FBBO Gold Member FBBO Gold Member

    Messages:
    20,999
    Likes Received:
    54609
    Joined:
    Apr 13, 2012
    Location:
    Granite Bay CA
    Local Time:
    1:04 PM
    I am having a hard time visualizing how all of this worked before but is screwy now.
     
  4. 1 Wild R/T

    1 Wild R/T FBBO Gold Member FBBO Gold Member

    Messages:
    3,823
    Likes Received:
    7502
    Joined:
    Jul 9, 2019
    Location:
    California
    Local Time:
    1:04 PM
    Have you tried unplugging the headlight switch with the relays plugged in?

    The headlights probably need at least 1.5 amps @ 10 volts to give off a dull yellow light... The relay will fully trigger with .05 amps @ 9 volts... So a trace voltage on the wires feeding the headlights wouldn't cause the headlights do anything but that same trace voltage will cause the relay to trigger & the relay will feed full voltage & full amperage to the headlights....
     
  5. Kern Dog

    Kern Dog FBBO Gold Member FBBO Gold Member

    Messages:
    20,999
    Likes Received:
    54609
    Joined:
    Apr 13, 2012
    Location:
    Granite Bay CA
    Local Time:
    1:04 PM
    That is a very interesting point. Rob/Crackedback suggested something similar. I will have to check that tomorrow. Small voltage running through the wiring that isn't enough to light up in the normal configuration but IS enough to trigger the relay. Hmmm.....
    I have not touched the headlight switch since I had the instrument panel out to reroute wires for the 5 speed swap. I suspected that the switch plug could be loose but I keep coming back to how the system works fine when undisturbed.
    I pulled the headlight door relay and looked at it. It looks like it could be just 5 years old....it is that clean. The spades are still shiny.
     
  6. blue69runner

    blue69runner Well-Known Member

    Messages:
    453
    Likes Received:
    508
    Joined:
    Jun 1, 2020
    Location:
    Lake Wales Fl.
    Local Time:
    4:04 PM
    If a relay is marked NC Normally Close means just that it is close. Normally open means it closes when you put power to the coil. NC opens when you put power to the coil it opens. If using relay's you need some expensive ones and need to know how many amp's your putting through them so you wont over load the contact's in them. Bought a relay for my radio amp and it was from the local auto part's store. They are cheap and lasted a short while so had to order one that carried more amp's and a bigger coil for duty hour ratting. All this being said. I would not worry about the headlight door as much as the head light's them selves. That is the big energy draw on the system. Hope this help's clear up the relay and how it work's.
     
    • Thanks! Thanks! x 1
    • 1 Wild R/T

      1 Wild R/T FBBO Gold Member FBBO Gold Member

      Messages:
      3,823
      Likes Received:
      7502
      Joined:
      Jul 9, 2019
      Location:
      California
      Local Time:
      1:04 PM
      I've always avoided the cheap relays, only use Bosch or Tyco.... On a recent project I used ten Bosch relays.... Seven of them were bad out of the box (I'd sourced them through Ebay so they could be knock offs).... The NO & NC (87 & 87A) contacts both had continuity with power (30) no matter whether the coil was energized or not....

      I had some Tycos (sourced through Waytek so I doubt they were knock offs) on the shelf so I grabbed them.... There was three bad relays in that box... I wound up using cheap Chinese relays & they worked.... Pretty bad when you have to test new components before installing them....
       
      • Like Like x 1
      • Thanks! Thanks! x 1
      • 1972GY8SE

        1972GY8SE FBBO Gold Member FBBO Gold Member

        Messages:
        1,476
        Likes Received:
        4193
        Joined:
        Jun 25, 2016
        Location:
        CA
        Local Time:
        1:04 PM
        You have a stray voltage in both high and low beam circuits (like R/T said), not enough amperage to power headlamps, but plenty enough to trigger relay coils; the beam selector switch has both these circuits in common. See the bottom of this diagram. Save it to your desktop and blow it up.
        Complete Wiring Diagram for 1970 Dodge Charger RT SE and 50.jpg
         
        • Like Like x 1
        • Thanks! Thanks! x 1
        • blue69runner

          blue69runner Well-Known Member

          Messages:
          453
          Likes Received:
          508
          Joined:
          Jun 1, 2020
          Location:
          Lake Wales Fl.
          Local Time:
          4:04 PM
          That is the truth. Golf cart relays are NO. Use same voltage to operate them. They have 12 volt and up ones. They handle a lot of voltage and amp's. Or relay's for solar panel operation's are heavy duty also. Went to school for electrical and was a job supper. For over 20 year's. Grew up in the pump and water business. Worked low voltage on sprinkler system's. Timer's and controls all my life. Some thing just dose not sound right and like some one said get a good meter and check the system out. If it where me I would use the wiring from the head light switch to turn on the relay and a good fused wire straight from the batterie to light the light's. You already have a switching means so use it and it wont take that much power to turn the relay on and off. This will keep the head light load of the wiring harness and your switches. When I get ready to do this will build my own system. Just my two cent's. Good luck you will get it figured out. If it worked for other's then it should work for you.
           
          • Thanks! Thanks! x 1
          • 1972GY8SE

            1972GY8SE FBBO Gold Member FBBO Gold Member

            Messages:
            1,476
            Likes Received:
            4193
            Joined:
            Jun 25, 2016
            Location:
            CA
            Local Time:
            1:04 PM
            This diagram is badass. Definitely a keeper.
             
            • Like Like x 1
            • 1972GY8SE

              1972GY8SE FBBO Gold Member FBBO Gold Member

              Messages:
              1,476
              Likes Received:
              4193
              Joined:
              Jun 25, 2016
              Location:
              CA
              Local Time:
              1:04 PM
              upload_2021-3-5_20-38-17.png
               
              • Like Like x 1
              • 1972GY8SE

                1972GY8SE FBBO Gold Member FBBO Gold Member

                Messages:
                1,476
                Likes Received:
                4193
                Joined:
                Jun 25, 2016
                Location:
                CA
                Local Time:
                1:04 PM
                upload_2021-3-5_20-41-4.png
                 
                • Like Like x 1
                • MoparGuy68

                  MoparGuy68 Well-Known Member

                  Messages:
                  549
                  Likes Received:
                  348
                  Joined:
                  Mar 31, 2019
                  Location:
                  Phoenix, AZ
                  Local Time:
                  1:04 PM
                  Looks like you’re having a lot of fun with this headlight relay thing. I was thinking about doing this to my car, but after reading this thread, I may hold off on attempting it for a while..
                   
                  • Like Like x 1
                  • Kern Dog

                    Kern Dog FBBO Gold Member FBBO Gold Member

                    Messages:
                    20,999
                    Likes Received:
                    54609
                    Joined:
                    Apr 13, 2012
                    Location:
                    Granite Bay CA
                    Local Time:
                    1:04 PM
                    If this is the case, what is the fix? Is it the headlight switch leaking power? Does that mean I'd need to replace that switch?

                    I don't know if my headlight switch is hot to the touch. You wrote "...now keeps my headlights flickering on and off..." Did you mean that now it keeps the headlights from flickering?
                     
                  • 1972GY8SE

                    1972GY8SE FBBO Gold Member FBBO Gold Member

                    Messages:
                    1,476
                    Likes Received:
                    4193
                    Joined:
                    Jun 25, 2016
                    Location:
                    CA
                    Local Time:
                    1:04 PM
                    Edit; Swap out the dimmer switch and retest.
                    If no change, use your meter and the diagram to back-trace the stray voltage.
                     
                    Last edited: Mar 6, 2021
                    • Thanks! Thanks! x 1
                    • 1 Wild R/T

                      1 Wild R/T FBBO Gold Member FBBO Gold Member

                      Messages:
                      3,823
                      Likes Received:
                      7502
                      Joined:
                      Jul 9, 2019
                      Location:
                      California
                      Local Time:
                      1:04 PM
                      As was mentioned earlier first confirm there is some sort of voltage on the purple or green wires in the stock headlight connector where the relay harness is plugged in with a meter, then as was pointed out by 1972GY8SE the floor mounted dimmer would seem like a good place to start looking, they commonly fail, they get dirt & debris in them from living on the floor, it's common for the connector to be cooked as well... But theres no power source to the floor switch until the dash switch sends it there so I doubt it's your issue....The dash switch would certainly be worth a look... And if nothings amiss there then either the bulkhead connector has issues (doubtful) or theres some cooked insulation inside either the forward light harness or the dash harness.... As Rob mentioned it could be a bad ground but that ground would be on something that is powered any time the ignition is on... You should pop fuses to isolate it down to a specific circuit..
                       
                      • Thanks! Thanks! x 1
                      • Agree Agree x 1
                      • Kern Dog

                        Kern Dog FBBO Gold Member FBBO Gold Member

                        Messages:
                        20,999
                        Likes Received:
                        54609
                        Joined:
                        Apr 13, 2012
                        Location:
                        Granite Bay CA
                        Local Time:
                        1:04 PM
                        That diagram prints but cannot be expanded without getting too blurry for me to see. I have factory service manuals and probably have the diagram out back. I'll grab it and see.
                        I checked Rock Auto and noticed that the Charger and Dart use the same dimmer switch. I have a few spares from various A body cars I've parted out over the years.
                        The other day before I installed this kit, I noticed that the headlight doors were open even though I didn't have the headlights on. I pressed the switch and the lights didn't come on. I pulled the carpet back and found that the plug to the dimmer switch was loose. After pressing it back in place, the headlights and doors worked normally until I installed the relays. I already pulled the steering wheel to get access to the underside of the dash so pulling the instrument panel is not much more work at this point.
                         
                        Last edited: Mar 6, 2021
                      • Kern Dog

                        Kern Dog FBBO Gold Member FBBO Gold Member

                        Messages:
                        20,999
                        Likes Received:
                        54609
                        Joined:
                        Apr 13, 2012
                        Location:
                        Granite Bay CA
                        Local Time:
                        1:04 PM
                        1) The forward harness was new in 2013 and still looks great but I will test.
                        2) Bulkhead has been cleaned and checked as recent as late 2019.
                        3) Power wire to the headlight switch was replaced in 2019.
                        4) Rob did mention the bad ground issue. The left side of this kit is attached to a point that also grounds the headlight harness and the engine block.
                        @Crackedback
                         
                        Last edited: Mar 6, 2021
                      • 1 Wild R/T

                        1 Wild R/T FBBO Gold Member FBBO Gold Member

                        Messages:
                        3,823
                        Likes Received:
                        7502
                        Joined:
                        Jul 9, 2019
                        Location:
                        California
                        Local Time:
                        1:04 PM
                        It's not the headlight ground thats the issue, it's power from somewhere else seeking a ground and going through the relay coil in search of that ground path...

                        And what ever that may be is only powered when the ignition is on.... Hence pull fuses.... Aftermarket stereo that ties into the dash light circuit?
                         
                        • Thanks! Thanks! x 1
                        • Agree Agree x 1
                        • 1972GY8SE

                          1972GY8SE FBBO Gold Member FBBO Gold Member

                          Messages:
                          1,476
                          Likes Received:
                          4193
                          Joined:
                          Jun 25, 2016
                          Location:
                          CA
                          Local Time:
                          1:04 PM
                          Follow the green wire.

                          upload_2021-3-5_23-24-2.png
                          upload_2021-3-5_23-30-20.png
                          upload_2021-3-5_23-36-59.png
                          Capture.PNG
                           
                          Last edited: Mar 6, 2021
                          • Like Like x 1
                          • Thanks! Thanks! x 1
                          1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
                            By continuing to use this site, you are consenting to our use of cookies.