1G 1G Headlights, Electrical gremlin or crazy engineering?

[Sbgriffin]

So I have a bit of an electrical conundrum I’m struggling with.

Recently I decided to upgrade my halogen headlights to LED’s on my 1ga with flip up headlights.
Found a kit with the proper sized headlights and a set of adapter harnesses. That way it can be wired to several styles of plugs. After following the directions and checking everything twice. I couldn’t get the LED’s to light up.
So I busted out my multimeter and did a few tests.

What I found is going from low beam to high beam. The polarity switches on me, the ground then becomes a positive. And one of the other terminals goes from negative to positive. If you look at the diagram I showed, the H4666 is the style of plug. For the life of me I can’t figure out what is going on.

Putting the Halogens back in, everything works fine, no fuse ever pops. But I do know that old school bulbs don’t technically have a polarity, they can work either way. So that’s my guess why it still works with the halogens.

Also I should state that I seem to have a considerable voltage drop and a fair amount of resistance on the ground. About a volt drop with the car running. Also I bench tested the LED’s, they light up fine on the bench.
So I’m just wondering if anyone has ran across a similar situation or has any ideas of what’s going on?
Thanks!

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[steve]

As you noticed the incandescent light don't have a polarity were LED lights do.

It's pretty well documented on the site that the DSM's use a switched ground circuit rather than a switched high circuit. This it the reverse of what your LED kit is designed for. On the DSM the Red/Blue wire going to both headlights is 12v from the headlight relay and the Red wire is the ground for the high beam and the Red/White wire the ground for the low beam. Those ground connections are from the headlight switch to the ground point.

You'll need some relays to reverse the polarity for the LEDs. That circuit uses the 12v from the headlight relay to provide switched power to two relays that are activated by the ground connections from the factory headlight switch.

 

[1990TSIAWDTALON]

Steve, would a 5 pole relay work for his issue. I am thinking it would as it is connected internally when not activated and when activated, goes to the other leg of the relay?
Is that what you were referring too also?

 

[steve]

Not sure what a 5 pole relay is (Actually I do but never on a car). The standard Bosch 5 pin relays are fine for this but you'll need at least two, one for high and one for low. Sometimes people use a set for each side. (I see now that some people out there incorrectly call this a 5 pole relay. So maybe this is what you meant.)

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Pins 85 and 30 would be connected to the +12v from the factory headlight relay (or just pin 85 and pin 30 with a fused wire from the battery if the lights draw lots of current, LEDs don't typically). Pin 86 goes to the switched ground from the headlight switch that used to go to the headlight. Pin 87 would go to the new headlight connector for whichever beam this is for and the headlight ground would go to a solid frame ground point.

When the headlight are turned on the headlight relay gets power and passes it along to one side of these relay's coils, the other side is grounded by the headlight switch. When the relay activates it switches 12v to the beam.

 

[1990TSIAWDTALON]

Glad you made sense of my nonsense. That is what I was trying to get at, a 5 PIN. Thanks Steve.

 

[steve]

They sell kits to do this like this one.

Amazon.com: True Mods H6054 H4 LED Headlight Wiring Harness [Negative Switched Conversion] [Fused] Universal H4 Head Light Relay Harness Kit for 9003 H6024 5x7 7x6 4x6 Subaru Toyota Jeep Sealed Beam Headlamp : Automotive

Buy True Mods H6054 H4 LED Headlight Wiring Harness [Negative Switched Conversion] [Fused] Universal H4 Head Light Relay Harness Kit for 9003 H6024 5x7 7x6 4x6 Subaru Toyota Jeep Sealed Beam Headlamp: Wiring Harnesses - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

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[CrackedDSM]

What kit did you get originally @Sbgriffin ? I will eventually upgrade my LEDs but I'm picky. I don't want the amazon fly's eyes three rows of 5 bulb headlights, nor do I want the "JDM" black housing with projector type look.

 

[Sbgriffin]

What kit did you get originally @Sbgriffin ? I will eventually upgrade my LEDs but I'm picky. I don't want the amazon fly's eyes three rows of 5 bulb headlights, nor do I want the "JDM" black housing with projector

Here’s the lights I went with off Amazon. I’m not sure if I like the style or not. Was really hoping for an improvement of light output and less amp draw. As the Halogens are quite lackluster…

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They sell kits to do this like this one.

Amazon.com: True Mods H6054 H4 LED Headlight Wiring Harness [Negative Switched Conversion] [Fused] Universal H4 Head Light Relay Harness Kit for 9003 H6024 5x7 7x6 4x6 Subaru Toyota Jeep Sealed Beam Headlamp : Automotive

Buy True Mods H6054 H4 LED Headlight Wiring Harness [Negative Switched Conversion] [Fused] Universal H4 Head Light Relay Harness Kit for 9003 H6024 5x7 7x6 4x6 Subaru Toyota Jeep Sealed Beam Headlamp: Wiring Harnesses - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

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Thanks Steve, I’ll look into that. I was leaning towards it being a switched ground circuit. I’ve wired several electric fans like that, so have a brief knowledge on how that works. I’ll have to decide if the juice is worth the squeeze on that.
Unfortunately I might have more issues than just that. I have excessive resistance on a few circuits and a voltage drop issue. A few years ago I accidentally hit part of the chassis harness with a sawzall blade. I repaired all the damage I seen. But I might have more than I had seen. I guess that’s more of a reason to rewire the headlights with a new sub-harness.
Thanks again for the info, gives me a good idea what I’m dealing with and where to go from here.

 

[Car Cannibal]

Great post Steve, I'm about to swap to H4 Hellas and wondered about the light wiring. It's been a tricky thing to navigate on older cars and high beams being 2 prong connectors.

Oracle has a cool ring light option for us 1ga so I'll get that wiring so it's plug and play.

ORACLE Pre-Installed 4x6" H4651/H4656 Sealed Beam Halo - All ColorsBlue

Product Description Features What's Included Installation Part Numbers Add Head-Turning Styling easily to ANY Classic with these high-quality Halo Headlight Replacement Lamps. Now you can even increase night time visibility by adding our LED Conversion bulbs (Part# S5231). These ORACLE head...

www.oraclelights.com