Headlight power source with relays.

Polara_500_Jr

Member
FCBO Gold Member
Joined
Aug 2, 2021
Messages
198
Reaction score
231
Location
MN/ND
So Tracing wiring I learned my dad had rewired the headlights of the Polara. Not surprised, we're both electrical minded people.
What I thought curious is that the 2 relays and fuses (high&low) are both mounted right under the battery on the left front of the engine compartment.
The power wires both wrap 3/4 of the entire area and look to have been tied directly into the alternator post.

Why there? all that extra wire, isn't it about equivalent to tying it straight to the battery? or was he pulling off the alt directly to save current on the charging circuit as well?

I guess I don't see a problem, so unless someone here has an explanation, maybe I just tie them back in there and hit the road.

Also, he still ran halogen bulbs. I will be converting to LED's soon enough, lower draw, better color and lumens :)
 
I’ve got mine straight to the alternator but my relays are hidden under the horns a foot away from it.
 
The Alternator seems to be the common place to source the power from since it is a stud that is easily accessible. Your dad more than likely didn't want to clutter up the battery post by tying in there. I would have done the same. Tie em back in and hit the road.
 
I tied my relays to a nice brass fuse bus right off the battery post. The alternator charges straight there too, via a bit of #8 wire with 6" of #12 fusible link at the terminal. My fuse bus gets the same, as does the starter relay. I use marine battery terminals with threaded studs to accommodate ring terminals, making the fusible links and the welding cable I run to the starter easy to connect or remove when needed.

12V circuits require one to minimize conductor lengths and/or oversize conductors beyond short distances to avoid significant voltage drops. I placed the headlight relays adjacent to the battery, with this in mind, and feed my pusher fan off the same bus. Each load gets a breaker which plugs nicely into the fuse bus clips.
 
Last edited:
Also, he still ran halogen bulbs. I will be converting to LED's soon enough, lower draw, better color and lumens
Yes the LED headlights do have lower draw, and better color.
But....
My experience LED headlamps is they have a shorter throw of light versus good quality halogens.
Also the older cars headlight buckets do not have the space and/ or room behind them as some LED headlamps have heat sinks or built on cooling fans.
Make sure you align the headlamps after installing your bulbs.

20230615_144636.jpg


20200526_210225.jpg
 
Yes the LED headlights do have lower draw, and better color.
But....
My experience LED headlamps is they have a shorter throw of light versus good quality halogens.
Also the older cars headlight buckets do not have the space and/ or room behind them as some LED headlamps have heat sinks or built on cooling fans.
Make sure you align the headlamps after installing your bulbs.

I use 60 yr old NOS EverReady* 4000 PAR lamps, which I scored a case of the low beams off eBay 6 yrs ago! I had to scour the Web for the matching high beam 4001s, but found a couple pair, so with good current and voltage, these American Beauties light the Road in the pearlescent optimum spectrum found by the DOT for human eyes at night. This light doesn't cause headache or glare blindness, unlike the blue-shifted spectra from too many LEDs. Folks notice it too.

I run NOS square-bear GE halogens in my '83 D150, but haven't got around to optimizing the headlamp circuit yet. The Good Lord willing, I shall by years end.

* Union Carbide/Westinghouse
 
Back
Top