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:
    54593
    Joined:
    Apr 13, 2012
    Location:
    Granite Bay CA
    Local Time:
    9:18 PM
    In 2013, I finally gave in to a friend that kept bugging me to modify my car to use relays to trigger the headlights.
    The car is a 1970 Charger with electric headlight doors.
    I don't recall the exact wiring changes but he intercepted the wiring paths and added one relay each for low beams and high beams.
    The changes messed everything up. The lights came on but wouldn't go off unless I hit the dimmer switch to engage the high beams. Another time, the headlights were on even with the ignition switch off. Again, hitting the dimmer switch turned the lights off and closed the doors.
    I knew very little about electrical stuff and the friend was equally confused. I ended up replacing the harness with a new Evans wiring section and the doors and lights worked properly again.
    In the years since, I have considered another try. I want brighter lighting and I want it street legal at a decent price. I figured that the first step would be to install one of the harness kits offered by FABO/FBBO member "CrackedBack". I ordered a kit and it arrived last week. I relocated the battery in the trunk in 2013 so I had room to mount the relays where the battery used to be.

    CB HL 2.jpg CB HL 3.jpg

    I ran the wires, attached the grounds and.....
    The headlights come on with the ignition key. The switch has zero effect on the lights or headlight doors. The dimmer switch does do it's job, high beams off or on. The headlight doors do not close. The headlights stay on when I shut off the ignition, but will go out by pressing the switch if the ignition is OFF.

    I emailed Crackedback and he responded quickly. He has made harnesses for many Mopars including the '70 Charger. He believes that the problem is likely a poor ground.
     
    • Like Like x 1
    • Thanks! Thanks! x 1
    • Kern Dog

      Kern Dog FBBO Gold Member FBBO Gold Member

      Messages:
      20,999
      Likes Received:
      54593
      Joined:
      Apr 13, 2012
      Location:
      Granite Bay CA
      Local Time:
      9:18 PM
      His words:

      "Most likely you have a ground path issue if the lights are staying on. The system is ground hunting back through the new harness is my guess. I've sold many kits for 70 chargers and yours is the only one that has this issue with the motors/doors/lights. All the factory wiring fires exactly the same way as OEM intended.

      With the headlight switch off, if lights are still on, pull the trigger plug out slightly and probe the three wires. The purple is low, green is high, brown is ground path. If the purple or green show any voltage, it's hunting a ground. Those lines are dead when switch is in the off position."

      I have limited experience with electrical stuff. I've soldered stuff, replaced damaged wires, eliminated ammeter wiring paths and stuff but diagnosing electrical systems is new to me. I have never heard of "Ground hunting" though I'm sure that it exists outside of my limited knowledge.

      After the weirdness today, I plugged the stock stuff back together and it worked like normal. AS far as I know, the wiring in the car works as intended.
       
    • Kern Dog

      Kern Dog FBBO Gold Member FBBO Gold Member

      Messages:
      20,999
      Likes Received:
      54593
      Joined:
      Apr 13, 2012
      Location:
      Granite Bay CA
      Local Time:
      9:18 PM
      Nacho rt74 wrote in a thread here somewhere:

      ".....on the concelead headlights, it takes the trigger source from the headlights coming from switch ( green wire ) to send the signal to open. When the headlight signal is off, the relay changes the points postion internally to feed the wire to close the doors. On these relays the relay is allways normally closed in one or another position. Is more like a selector to feed one or other function when is being triggered or not. I can't recall the color functions on the headlight door motor, but I think both wires for close and open the doors are black, one with red trace and the other with yellow trace ??????? dunno. Blue wire is the RUN circuit, to make work the doors just with the RUN circuit as a power source."
       
    • 66 Sat

      66 Sat Well-Known Member

      Messages:
      944
      Likes Received:
      1549
      Joined:
      Apr 26, 2015
      Location:
      Australia
      Local Time:
      11:18 PM
      Spend $100 and take it to an auto electrician.
      I hate dealing with electrics and although I'm all for learning new stuff, sometimes it's better to let someone who does this day in day out do it properly.
       
      • Thanks! Thanks! x 1
      • Nacho-RT74

        Nacho-RT74 FBBO Gold Member FBBO Gold Member

        Messages:
        4,555
        Likes Received:
        1544
        Joined:
        Oct 8, 2012
        Location:
        Valencia, España
        Local Time:
        6:18 AM
        Just thinking out loud... swap around the relays to check if something changes.
         
        • Thanks! Thanks! x 1
        • mccoymail

          mccoymail Well-Known Member

          Messages:
          426
          Likes Received:
          283
          Joined:
          Nov 30, 2010
          Location:
          Johnstown, Ohio
          Local Time:
          12:18 AM
          I have both kits on my 70 Charger and they work fine. I do recall that i had to do some head scratching on the door relay. If you'd like, I can crawl around and walk you through what I have done. PM me
           
          • Thanks! Thanks! x 1
          • 747mopar

            747mopar FBBO Gold Member FBBO Gold Member

            Messages:
            12,696
            Likes Received:
            16125
            Joined:
            Oct 30, 2012
            Location:
            ohio
            Local Time:
            11:18 PM
            A setup like this is extremely easy to sort out, to wrap your head around it it's best to draw it up and understand how it works/supposed to work first. Study relays and understand them, once you get it it's super easy. If your unsure on how they work just ask, one of us will explain it. If you don't own a voltmeter buy a decent one.
             
            Last edited: Mar 5, 2021
            • Agree Agree x 2
            • Thanks! Thanks! x 1
            • 6PKRTSE

              6PKRTSE Well-Known Member

              Messages:
              1,917
              Likes Received:
              2722
              Joined:
              Nov 15, 2010
              Location:
              Motor City
              Local Time:
              11:18 PM
              Think I posted about mine before. I used cracked backs relay kit on my 70 with no issues. It also eliminated my extremely hot to the touch headlights switch and now keeps my headlights flickering on and off when on high beams. All lights are much brighter.

              20210128_191817.jpg 20210128_191639.jpg
               
              Last edited: Mar 5, 2021
              • Thanks! Thanks! x 1
              • 69Bee

                69Bee FBBO Gold Member FBBO Gold Member

                Messages:
                2,660
                Likes Received:
                2305
                Joined:
                Nov 17, 2009
                Location:
                Whetstone, AZ
                Local Time:
                9:18 PM
                I looked up a circuit, and one thing I notice (not saying yours are), is that the power goes to the common terminal. The lights should go to the common terminal on the relay, and the relay should switch from gnd (NC) and power should be on the NO terminal. Power shouldn't be switched, but rather the light, and when off, the light is grounded. Also, there are no diodes for voltage spike suppression.
                 
                • Like Like x 1
                • Thanks! Thanks! x 1
                • Kern Dog

                  Kern Dog FBBO Gold Member FBBO Gold Member

                  Messages:
                  20,999
                  Likes Received:
                  54593
                  Joined:
                  Apr 13, 2012
                  Location:
                  Granite Bay CA
                  Local Time:
                  9:18 PM
                  Thanks but I don't understand any of that!
                   
                • 69Bee

                  69Bee FBBO Gold Member FBBO Gold Member

                  Messages:
                  2,660
                  Likes Received:
                  2305
                  Joined:
                  Nov 17, 2009
                  Location:
                  Whetstone, AZ
                  Local Time:
                  9:18 PM
                  No problem. The circuit I found for automotive headlights looked like it was not designed by someone with electronic experience, or just didn't care how well it worked.
                   
                • Kern Dog

                  Kern Dog FBBO Gold Member FBBO Gold Member

                  Messages:
                  20,999
                  Likes Received:
                  54593
                  Joined:
                  Apr 13, 2012
                  Location:
                  Granite Bay CA
                  Local Time:
                  9:18 PM
                  This is probably like other things that confuse me. I'll be sitting or doing something simple and the whole issue will start to make sense.
                  The mind is an amazing thing
                  So often, I try to force myself to remember something. Most of the time I can access whatever memory I need. Other times there is a block that just disappears without reason and I remember what I need. I'm sure this happens to others.
                   
                • Nacho-RT74

                  Nacho-RT74 FBBO Gold Member FBBO Gold Member

                  Messages:
                  4,555
                  Likes Received:
                  1544
                  Joined:
                  Oct 8, 2012
                  Location:
                  Valencia, España
                  Local Time:
                  6:18 AM
                  I'm wondering how will act everything with harness connected and without relays... or alternating just one relay conected, then the other... and so.

                  Maybe even with relays conected but no headlights
                   
                  • Thanks! Thanks! x 1
                  • Kern Dog

                    Kern Dog FBBO Gold Member FBBO Gold Member

                    Messages:
                    20,999
                    Likes Received:
                    54593
                    Joined:
                    Apr 13, 2012
                    Location:
                    Granite Bay CA
                    Local Time:
                    9:18 PM
                    It is still screwed up.
                    I moved one ground wire, the one for the drivers side. It now is on the engine side of the core support, the spot where the battery negative 8 gauge wire usually attaches as well as the stock headlight ground point. The lights still come on when the key is turned but do go off when the key is shut off. This means headlights on all the time the engine is running. It is like the headlights have no connection to the dash switch once the key is on. With the ignition ON, pressing the switch does nothing.
                    W T F ??
                    With the key off, the switch works the headlights normally.
                    With the key ON, the headlights come on without touching the switch. They do not go off until the key is tuned off.
                    Pressing the dimmer switch makes no difference other than doing what it is supposed to do, activate the high beams then deactivating them.
                    Bonehead diagnosis here.....
                    The relays are supposed to wait until the headlight switch "asks" for the lights to come on. The relays are supposed to have power waiting for the switch. Right now, the system just assumes the headlights want to come on once the key is turned.
                     
                  • 1972GY8SE

                    1972GY8SE FBBO Gold Member FBBO Gold Member

                    Messages:
                    1,469
                    Likes Received:
                    4150
                    Joined:
                    Jun 25, 2016
                    Location:
                    CA
                    Local Time:
                    9:18 PM
                    I just realized this was a "plug and play" kit, so I deleted my post.
                    If you still need help, PM me, I can walk you through diagnosing the issue.
                    Meanwhile--I have to some yard work to do.
                     
                    • Like Like x 1
                    • Thanks! Thanks! x 1
                    • Kern Dog

                      Kern Dog FBBO Gold Member FBBO Gold Member

                      Messages:
                      20,999
                      Likes Received:
                      54593
                      Joined:
                      Apr 13, 2012
                      Location:
                      Granite Bay CA
                      Local Time:
                      9:18 PM
                      There is an error when I tried to send a PM to 1972 GY8SE.

                      This thing is pissing me off.
                      I added grounds to the stock headlight plug socket grounds. No change.
                      I swapped relays side to side. No change.
                      I tried different relays. One headlight stayed on with the key off, indicating to me that the relay was stuck open. Putting the new relays back in, it was back to the weird symptoms described earlier.
                      The headlight relay in the dash is clean, the spades are clean, the attachment screw is tight.
                      I unplugged the headlight door motor. No change.
                       
                    • Kern Dog

                      Kern Dog FBBO Gold Member FBBO Gold Member

                      Messages:
                      20,999
                      Likes Received:
                      54593
                      Joined:
                      Apr 13, 2012
                      Location:
                      Granite Bay CA
                      Local Time:
                      9:18 PM
                      I found these diagrams in my files.

                      70-71_HEADLAMP_RELAY_DIA.gif
                      Below is something I recall that I saw as a replacement for the stock relay using a commonly available 30A relay.


                      1970_Charger_headlight_door_relay_upgrade.JPG
                       
                    • Kern Dog

                      Kern Dog FBBO Gold Member FBBO Gold Member

                      Messages:
                      20,999
                      Likes Received:
                      54593
                      Joined:
                      Apr 13, 2012
                      Location:
                      Granite Bay CA
                      Local Time:
                      9:18 PM
                      Ever have that moment where you find out that all along, YOU were the problem?
                      I'm not sure if that is the case here but it might be.
                      In 2013 when I moved the battery to the trunk, the lead positive cable that I used was ran through a FORD solenoid so that it is dead except when cranking the engine. The positive cable comes off of the battery and to one side of the solenoid and picks up on the other side. From there, the cable routes through the inside of the car and attaches directly to the starter. I have a small section of 10 ga wire connecting the 2 terminals on the starter so that when power reaches the starter, it always spins.
                      To trigger the starter, I ran a trigger wire from the starter relay on the firewall back to the Ford solenoid.
                      With the key off, there is no power to the starter relay or to the alternator stud. I checked my Power Wagon and found that with the key off, the alternator stud is live and the starter relay big lug is too.
                      I wonder if this relay kit somehow is dependent on constant power. Maybe I can rig up another battery to see.
                      **************************************************************
                      E D I T:
                      What a mess.
                      I used the test light on the Power Wagon to see if the alternator and starter relay had power with the key off, THEN checked the car. Somehow in the 25-30 steps I took, the bulb in the test light must have burned out. I grabbed my voltage tester and confirmed that even with the wiring changes in 2013, the alternator stud and starter relay do have power at rest. Christ, this is frustrating.
                       
                      Last edited: Mar 5, 2021
                    • Nacho-RT74

                      Nacho-RT74 FBBO Gold Member FBBO Gold Member

                      Messages:
                      4,555
                      Likes Received:
                      1544
                      Joined:
                      Oct 8, 2012
                      Location:
                      Valencia, España
                      Local Time:
                      6:18 AM
                      Yeap, I made a diagram about the diff options for the diff relays available sometime ago

                      hideaways-hook-up-d-jpg.jpg

                      Recently a Ford relay was posted at DC.com board working the same and no needing a ground wire since the housing works as ground just like the original one.
                       
                      • Thanks! Thanks! x 2
                      • Crackedback

                        Crackedback Well-Known Member

                        Messages:
                        359
                        Likes Received:
                        331
                        Joined:
                        Aug 12, 2008
                        Location:
                        Southern California
                        Local Time:
                        9:18 PM
                        I suggested that the car is hunting for a ground and it is using the new harness to find one. It's not a ground issue with my system from what you wrote. This is a classic ground hunting situation similar to a marker light staying on when the switch is off.

                        This is the first and only 70 Charger out of maybe 50 I've built kits that has had this issue.

                        Please do what I suggested in my first email response on the trigger wires. If ANY of those wires show voltage, particularly the green or violet, even the slightest bit, you likely have an issue with a ground SOMEWHERE else on the car. Your headlight switch controls EVERYTHING in the triggering. If the switch is off, energy is coming from somewhere in err. My kit is essentially stand alone from the rest of the car and the only OEM thing it uses is the low beam headlight plug to provide a relay trigger signal.

                        There are a lot of changes to the car which is fine. Have a bunch of kits in service that have batteries in trunk too.
                         
                        • Thanks! Thanks! x 1
                        • Agree Agree 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.