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Hi all. This question is specifically about the 12 volt, positive ground system in my 1955 Packard, but I'm guessing the general principles would apply to any positive ground Packard (or other car or truck), 6 volt or 12 volt, using a single sealed beam headlamp on each front fender.

I had to replace the crusty headlamp wiring harness in my car, as the cloth wire wrapping was flaking off and it was shorting out against the radiator support. While I was in there, I decided to try Holley's new RetroBright LED 7" headlamps. They fit just fine into the 1955's buckets, with zero modification needed. The reproduction headlamp harness connected right to the lamp, and all I needed to do was to attach the wires per the wiring diagram to the new junction blocks I got from Dwight Heinmuller.

Unfortunately, the headlamps wouldn't light. I had power from the battery and I had all my interior and exterior lighting illuminated when the headlight switch was pulled out to the first position. However, pulling the switch out to the Headlamps position resulted in no forward lighting whatsoever. The dash lights and side running lights and tail lamps were still lit, the parking lights turned off just like they should, but the headlamps remained dark.

I tried exchanging the positions of the BR-Brown and LT.G-Light Green wires from the headlamp harness on the junction block in case there was an issue of polarity inside the LEDs, something I'd run into before with a 2001 Camaro SS, but that also did not work.

Finally it was time to call in the big guns, and I appealed for help from one of my friends who is an electrical engineer. He spent a few minutes with it, swapped the ground wire and the low beam wire on the junction block, and the headlight came on! The bad news is that this arrangement would only allow me to use the low beams.

My question to our group is -- has anyone else used the Holly RetroBight on your positive ground car? What did you have to do to get both beams operational? Or are you getting by just with the low beams? It seems to be an issue of needing two ground wires instead of one, so that I would have a ground wire to also swap with the high beam wire on the junction block. I would then end up with the BR-Brown and LT.G-Light Green wires fastened to the fender splasher with a screw where the black ground wire used to be.

Admittedly, I don't see myself driving my car anywhere that late at night and needing the use of high beams, but I'm one of those OCD guys who thinks everything should operate properly as designed! Any help and advice would be welcomed!

Attached is an excerpt of the 1955 wiring diagram, edited to focus just on the forward lighting.

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1955-56 Headlamp Wiring Diagram.pdf Size: 63.50 KB; Hits: 87

Some have changed car polarity on 55s and if you wanted to do that, as long as the rest of the car is stock and you have no solid state replacements such as radio vibrator or TL switch it is usually a relatively easy thing to do. Normally it only requires swapping cables along with a small procedure and couple of minor wire swaps but if you have a polarity sensitive voltage regulator that might need to be changed too.

I am generally in favor of adding relays to the headlight circuit to take the heavy light current out of, and hopefully prolong life of, the old switches. An added benefit is you can use heavier wire for the headlight feed and that combined with eliminating about 10 ft of smaller gauge wire would give a brighter light. Obviously there would not be nearly as much current with LEDs but the principle holds so if you want to keep polarity stock, relays are another option.

Since you could reverse wires at the lights and have one beam work it would appear a modification of a basic relay circuit would do the job on your lights. As long as the LED internal headlight functions are not interconnected in some way and they have a separate normally negative ground wire and that wire is not connected to any body metal via some kind of bracket It would be a simple matter to make a couple of changes in the relay wiring to swap how voltage and ground enters the headlights to maintain the Hi-Lo function.

Here is a modification of a basic relay diagram and a photo of a relay module. Changing relays to use 6v or 12v relays it could be used on most years. In place of the circuit breaker normally connecting to the relay, for the negative ground LEDs wiring was changed so it now has the breaker carrying negative battery voltage connecting directly to the LED bulb negative ground wires. The relays now switch the Hi and Lo leads to ground for the Hi-Lo function.

For my 56, on the relay module shown the terminal strip is a bit different from the diagram because I decided to also have the ground wire connect there. It was placed on the Left side with a new cable running across to the right side headlight. Left light connects directly to the new relay terminal strip along with the new wire to the right. I added a new Right side terminal strip but the original head light wires from the loom to the old right terminal block could be disconnected and protected so that terminal strip could be used instead. The functions in the parking light housing are still connected on the old right strip.

There is a way to keep the original loom and terminal strips in use but it would mean disconnecting wires at the dimmer switch, finding a splice point for the wire going to the brite indicator lamp and then adding relays down at the dimmer switch. I think it would be easier to just add relays in front and a length of 3 wire cable to the right light. Run that cable under the upper splash panel and clamp to the cradle in front of the radiator.

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Before you reinvent the wheel, why don't you call the manufacturer or look on the website. I'm sure they can tell you one way or the other, if you get tech service.
Alternately, ask where you bought them.

It's nearly impossible to tell over the internet if you have it hooked up right or other faults or how to fix and what technology they employ. Holley doesn't make them so they're a licensed reseller most likely.
When installing modern technology in 67 year old technology - expect some difficulty and plan it out before one proceeds.

I typically use Vintage Car LEDs which have a similar look to the originals, especially if you choose the Economy lens option. They work with either polarity.

Something I wonder about the Holley lights is if they are DOT approved. Didn't see anything on their website but the Vintage Car site says theirs are not and to protect themselves their lights are sold for "off road use only".

Earlier this year I read there was a push to finally get the US to update and adopt world standards so European cars did not need special lights that were inferior to their E standards to be sold here. The change, I believe, was supposed to be introduced as one of the specialty items in one of those huge funding bills up in congress earlier this year.

I don't remember reading if it was included or if the proposal is still being studied to death. Anyone know if the US has gone modern or is at least trying to catch up with the rest of the world?

I don't specifically see the language "DOT Approved" on the Holley website. The closest I can find is "Compliant - No-glare beam pattern meets or exceeds SAE and DOT Requirements." Conversely, there is also zero mention of "Off-Road Use Only." So, there's that...