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Headlight relays on a car with concealed headlights

Kern Dog

Life is full of turns. Build your car to handle.
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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.
 
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.
 
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."
 
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.
 
Just thinking out loud... swap around the relays to check if something changes.
 
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
 
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.
 
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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
 
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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.
 
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.
Thanks but I don't understand any of that!
 
Thanks but I don't understand any of that!
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.
 
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.
 
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
 
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.
 
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.
 
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.
 
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
 
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.
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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.
 
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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.
 
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.
 
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