Headlight relays on a car with concealed headlights

[Kern Dog]

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 **** 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.

 

[1 Wild R/T]

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...

 

[Kern Dog]

I am having a hard time visualizing how all of this worked before but is screwy now.

 

[1 Wild R/T]

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....

 

[Kern Dog]

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....

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.

 

[blue69runner]

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.

 

[1 Wild R/T]

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.

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....

 

[NoCar2023]

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.

 

[blue69runner]

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.

 

[NoCar2023]

This diagram is badass. Definitely a keeper.

 

[NoCar2023]

 

[NoCar2023]

 

[MoparGuy68]

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..

 

[Kern Dog]

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.
View attachment 1079420

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?

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.

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?

 

[NoCar2023]

Edit; Swap out the dimmer switch and retest.
If no change, use your meter and the diagram to back-trace the stray voltage.

 

[1 Wild R/T]

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..

 

[Kern Dog]

Yes, swap out the dimmer switch and retest.
If no change, use your meter and the diagram to back-trace the stray voltage.

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.

 

[Kern Dog]

.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..

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

 

[1 Wild R/T]

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?

 

[NoCar2023]

Follow the green wire.