Is there a reason that the (+) Power is connected at the alternator and not directly off the battery?

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1964 Dart GT

Less voltage drop. If the wire from the alternator to the battery is sufficient it matters little either way.

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Joshua

Speaking as the one who drew that diagam many years ago, the answer is no. And I really ought to redraw it (with something more modern than MacPaint) because while the alternator B+ terminal and the battery positive terminal are electrically common, what you get at the alternator can tend to be somewhat noisier/spikier (particularly on our cars with their primitive voltage regulation) than what you see at either end of the positive battery cable. Sometimes a little voltage drop is a good thing; if you run your headlight bulbs on spiky 14+v from the B+ terminal, they'll die sooner than if you pick up your power off a cleaner/smoother source.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Just going to tag on to this thread (as I figure out how to move my headlight relay wiring to the battery)

Dan -I found the following micro dual relays for mounting on a PCB board.
http://www.pickercomponents.com/select-a-relay.php#!prettyPhoto

Based on my limited knowledge they appear that they could handle the switching duties for the headlights.

What is your opinion on the manufacture and the form factor?

Thanks in advance for your comments

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1975 Dodge D100 Utiline
Slant 6, Super Six, Weber 38, 727
Repair work in progress.

And if the relay breaks in the middle of nowhere..........


This relay pretty much available anywhere:

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Thanks everyone! Having moved the alternator over to the drivers side the (+) Battery cable (from the Alternator) is Very Short now, and I have Battery terminals that allow for accessory connections.

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1964 Dart GT

I'd answer if I knew which relay on that page you're looking at. I'm unfamiliar with that manufacturer. And I don't agree with using printed circuit boards for this application.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

So based upon the existing drawing, if the relays were powered from the positive battery cable, would the power to the relays be appreciably less spikier?

Or is there another better, more modern way to configure the circuit so as to reduce the spikes?

As always, thanks for your input.

Neil

Yup, correct -- things are a little less noisy at one or the other end of the battery positive cable than at the alternator output. On the other hand, using the alternator B+ terminal means you're drawing headlamp current upstream of the bulkhead connector, reducing the load on this notoriously low-test part of the car's electrical system; that's a very good thing and worth some reduced headlight bulb life due to somewhat "noisier" input.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I made an alternator direct to battery amp gage bypass shunting all charging amps directly to battery bypassing bulkhead, rendering amp gage to read only battery to load amperage (that would be shown as a discharge). Lighting relays are triggered by old headlight circuits (high & low beam) drawing current directly from battery to feed headlights. I also installed a secondary front of car lighting ground loop of #10 conductor connected directly to negative battery terminal the other half of the lighting circuit. Result of this circuit rework has been much brighter GE Night Hawk lamps, and no big amp load through headlamp switches & bulkhead connector.

Small print disclaimer: Dan supplied quality relays, lamp sockets, and terminals.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Sorry about the link. Didnt check it before I posted.

Here is the link to the data sheet for the relay I was looking at.
http://www.pickercomponents.com/pdf/Relays/PC549-30-Amp-Ultraminiature-Automotive-PCB-Twin-Power-Relay.pdf

What are your objections to using a printed circuit board?

I was mostly thinking of using this on my Honda CX500. I currently have it wired with two bosch relays but was looking for something more compact.

Thanks again for your sage advice

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1975 Dodge D100 Utiline
Slant 6, Super Six, Weber 38, 727
Repair work in progress.

In car/truck type service, a PCB is a needless complication that hinders system repair and component replacement. In a motorcycle application, it might make sense for the compactness. Still no data on this relay maker, but the specs look nice.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I put the relay for the light under the seat on my motorcycle.......

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

great and all I did the headlight relay with my old 6012 lamps that layed around enough years (8+) the sealed beams got some water in them but they're both much brighter. I got manufactures coupons from GE for their poor quality explosive-light/your house on fire quality lightbulbs, if their GE Night Hawk light bulbs are decent, lets see how long they last. GE is manufacturing over seas with no quality control. Because they're quality control is run by some Hungarian who hasn';t understood $#!+ about lighting since 194x.

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exoJjL

The Night Hawks were recommended by slant6dan as a cheapo alternative due to their better Lenz stamping; I'm sure he will refresh our collective recollection's on the exact reason.

As for GE Q control, my mechanical engineer son is one of those guys for the Bangor Maine turbine rebuilding complex where GE turbines from the around the world are sent to be rebuilt.

I got a tour of the place a few years ago and saw a lathe that can handle a 400 inch long 38 ton chunk of metal, and turn it within in a few ten thousands of an inch located in a temperature controlled environment.

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67' Dart GT Convertible; the old Chrysler Corp.

82' LeBaron Convertible; the new Chrysler Corp

07' 300 C AWD; Now by Fiat, the old new Chrysler LLC