A few melted spots in headlight harness

[HTMLmopars]

Driving my 68 Valiant the other night, the headlights crapped out, but the brights still worked. Went under the dash the next day to investigate and noticed that all 3 wires going to the dimmer switch were melted together. I had previously replaced the switch, so all the connections were ones that I had made. Remade all the connections, everything worked again, but whenever I have the headlights on, I can smell the beginnings of those wires melting back together. Today I went to chase the problem down and pulled the headlights, passenger side was good, but driver's side had the red lead's housing looking kinda melty, not super bad, but enough to make it harder to remove. So if I'm not mistaken, this points to the driver headlight being the problem? Running cheapo aftermarket halogens, just bolted them in place when I was 16, never thought twice about it. I'm thinking about buying new headlights soon, do yall think the halogens are what caused the problem, or just old car with shoddy wiring?

 

[72bluNblu]

The cheap halogens probably aren’t helping. Sounds like it’s time to talk to @crackedback about a new headlight harness.

 

[crackedback]

Sounds like a dead short somewhere. The light could be the problem. GE Nighthawks are solid headlight for a 2 headlight car. Not expensive either.

Check the wires anywhere they are close to two panels bolted together for any pinching. If it's melting all three wires together, something is going very badly.

 

[Mattax]

this points to the driver headlight being the problem? Running cheapo aftermarket halogens, just bolted them in place when I was 16, never thought twice about it. I'm thinking about buying new headlights soon, do yall think the halogens are what caused the problem, or just old car with shoddy wiring?

a. Yes - probably the halogens are causing a higher current draw than originals. However some halogens actually draw less than original. Look at the number and we'll know which lamp is in there. 6012, H6014, or H6024
b. Look for insulation damage where the wires come through the headlight buckets. I've had that where the wire insulation had rubbed through and contact a second wire or even ground. If it grounds it should trip the circuit breaker, but maybe too late.
c. Probably want to redo your repairs - we all learn to do better.

d. Yup add a relay harness. Well worth it. The a-body headlight wiring wsa only 16 and 18 ga. really minimal.

 

[Mattax]

Probably want to redo your repairs - we all learn to do better.

Might need need new connectors and terminals.
Look first. Then decide.
Make sure you get the correct terminals and a crimper for the 'open barrel' wings that hold the wire and insulation.

The nighthawks are good, as are a couple of the H4s (more expensive) but they all draw more than the system was designed for.

 

[RedFish]

In my 67 fish, I have aftermarkets 7 inch round plastic housings with bulb poked in the back. OEM connectors onto that would crush against the back of the bowl. I suspected it could become a problem. Replacement offset / flatter configuration connectors cured it. Dorman 84790

 

[Demonic]

If it got that warm, the whole harness has damage. I'd replace all the headlight wiring on the engine side, and maybe individual wires to the dimmer switch. Or convert to relays, as others mentioned.

 

[RedFish]

I added relays when I installed thees light fixtures. The higher current would only make matters worse in event of short circuit. Headlight switch has a cycling circuit breaker inside rated at 15 or 20 amps, protecting entire circuit from switch to bulbs. It should prevent catastrophic meltdown. Relays render it useless if the fault lies beyond the relays. Locate the fault first. good luck

 

[Dana67Dart]

loose contacts as Matax noted increase the total resistance in the system and will then increase the current going thru the wires and other connectors. Replacing the headlight switch connector right now (67 dart) it had the B1 connector melted and recently lost connection. cleaning and tightening the connectors and replacing the plastic connector should be my fix for another 50 years.

 

[4spdragtop]

Im redoing my harness and have spotted a few dimmer connectors that have shown some heat damage. Also the wires are usually stiff/damaged. I plan on replacing and possibly upsizing the wires.
As to the reason why.....multiple reasons, but 1 I think that hasnt been mentioned is our dimmers are on the floor under carpeting. I believe any moisture gets trapped there and causes shorting. Also our clumsy feet knocking around the dimmer probably doesnt help.

 

[Mattax]

Larger wires can help reduce overall resistance in the circuit, but notice where the damage occurs.
What does that tell us?

Damage occurs where the most heat is generated. So that was either or both:
* Location where resistance to flow was higher.
* Place where heat couldn't dissipate so it got hotter.

The connections are almost always the location of highest resistance.

Heat damage also is cumulative on the terminals and the wire.
The insulation gets worse and maybe more important, surface contaminants burn and oxidatiion build up is worse.
Clean the terminals and crimps with some deoxit or similar. Tighten the crimps and loops if needed, and/or replace if bad.

I think if a car never got the newer 6014 headlamps, there would have been less headlight circuit issues. But after 10 years most cars have had the headlights replaced, and what was available was rarely the older 6012s. I had the circuit breakers trip off on my a-bodies in the mid 1980s. Car was only 15 years old.

 

[HTMLmopars]

The cheap halogens probably aren’t helping. Sounds like it’s time to talk to @crackedback about a new headlight harness.

I'm thinking that this might be the best plan. Didn't really want to spend a bunch of money, but in the end, lighting is something that's worth not skimping on, especially on a car that I'm driving across Washington in all the time.

c. Probably want to redo your repairs - we all learn to do better.

Once I saw how bad the wires were, I remade the connections. Also this car lives outdoors in the PNW and gets wet floors frequently, so I doubt that helped. She's garaged in Spokane right now, hoping to be able to move into a place with a garage after I "graduate". At home, my dad's 68 Charger and grandpa's 56 Metropolitan get the garage space.

 

[RustyRatRod]

Get the harness @crackedback makes and you'll never have to worry about that BS again. It takes all the load off the switch and puts it on the relays where it belongs.

 

[Mattax]

Once I saw how bad the wires were, I remade the connections. Also this car lives outdoors in the PNW and gets wet floors frequently, so I doubt that helped. She's garaged in Spokane right now, hoping to be able to move into a place with a garage after I "graduate". At home, my dad's 68 Charger and grandpa's 56 Metropolitan get the garage space.

If you used the standard parts store terminals, they're not great. Crushing the barrel isn't usually as strong and tight of a connection as the factory type. And the factory type has support for the insulation.
Headlight connectors have a wider spade and need a wider terminal than the typical Packard 58.
Sources for Chrysler type wire terminals
Take the time and recheck the insulation through the buckets. Having the lights go out at night is never fun!

You don't have to spend the big bucks for Cibie, or even the Hella 'Vision Plus' H4s.
The GE Nighthawk sealed beam in 7" round is pretty good. They do have shorter life so buy an extra and they do draw more current on low beam than regular 6014 or 6024s
IIRC they are sold as H6024NH.
You can buy a relay harness from Crackedback all made up and ready to plug in. You just need to rout it, plug into one of the existing headlight connectors, and connect the fused power to the alternator output stud. That will take the electric load off the original headlight circuit.
If you prefer to make your own, starting with a kit from Daniel Stern will get you good quality components.

I made my own over 10 years ago. That me run H4s even though the headlight connector looked like this.

The relay system works with a damaged circuit because it takes less than an amp to turn on the relay.

 

[Mattax]

Look at the headlight circuit and you can see how long the path is from the alternator to the lamps.
Also see all the connections the power has to flow through.

Relays are electrically powered switches.
Turning the headlight on with the headlight switch now sends a little current to the relay.
The 9 plus amps for the headlights then go from the alternator through the relay to the lamps.
Look how much shorter the run is, avoids most of the hot engine compartment, involves fewer connections and can use heavier wire.

 

[HTMLmopars]

Thinking I'm gonna just bite the bullet and pick up the new harness. It'll be good to be able to trust at least some of the wiring on the car, and then I shouldn't have to worry about headlight problems again. I've learned to buy quality rather than patch and patch and patch the cheap stuff