66RBS

Re 66
I have been planning on doing the headlight relay upgrade. Not sure if I'll upgrade to H4 halogens or not as I drive the car rarely at night.
My objective is to minimize the voltage drop on my original wiring and get max lighting from the sealed beam halogens the few times I do drive at night.

My thoughts were to run #14 gage wire from the relays to the headlights but looking at the buckets this seems like a lot of work ( pull the buckets ?) to get the larger wire to the lamp buckets.

What if I run 14 Ga wire from the relays to the factory headlight extensions ( 18 ga). Will I still get voltage drop if I use the 18 ga headlight extensions?

So as not to cut up the original wiring I plan on taking the coil signal from the headlight connector at the radiator support, mount the relays on the front of the radiator support and pull 12 v power (14 ga.) from the horn relay.

Anybody done before and after voltage drop measurements with the 18 ga wire?

Randy

DUB

First off...you DO NOT have to pull the buckets to get new wire into the pivot. but...I know how to do this so it is not a big deal. I have all correct wire terminals and crimpers...so having the correct tools does make it work better for me.

I know companies sells the relay kits...and I have installed my own relay set-ups.

One thing that I do...is I first check to see how many amps the headlight system is currently drawing when used. Then I check the new lights and see what it draws. Then looking at the alternator...it may need to be upgraded....along with the wire that gets attaches to the back of the alternator MAY NEED to be increased in gauge size to accommodate the amp draw increase. Because.... adding large gauge wires at the horn relay connector....and the power supple wire still being what it is...is somewhat pointless.

I am more worried about the amp load on the wires...and their length. Kinda like your battery cables...they carry 12 volts+...but it is the AMPS that require them to be a large gauge size....because if volts is all a person would need to be worried about....then battery cables could be small wire like that for running home phone lines....which we know they can not...because they would fry.

DUB

BADBIRDCAGE

When I did my relays I ran a 6 ga cable from the hot battery terminal to an after market, six fuse block. Then pulled a 10 ga supply line from the fuse block to each relay. I used the high and low beam factory feeds from the dimmer switch to excite the relays.

59BlueSilver

Does anyone have a wiring diagram of this? I'd like to add relays to my headlights also.

856666

There are many good posts on this topic - Relay-

https://www.corvetteforum.com/forums...-question.html

The key is to first check your voltage at the headlights with everything running/on and engine running at fast idle - and compare this voltage to Ault. output - should be very close. If not install relay's.

Phil

Frankie the Fink

Note that along with the pictures in the linked thread above (post #5) the author correctly took the relay hi-current feed off the car's horn relay power buss. THAT is where the regulator senses current and adjusts alternator output accordingly - this ensures the alternator is set up to deal with the 'true' current draw which isn't sensed at the battery "+" terminal.

66RBS

Thanks Frankie. Yes I plan to pull the power from the horn relay as it will shorten the length of the wiring. Also technically correct as you point out.
On another note, I noticed the headlight extension for the driver's side bucket is 18 Ga and for the passenger side it is 16 Ga. At least on a 66 it is. That must have saved GM millions

Randy

66RBS

Phil,

Ran a test for some voltage measurements

At 1000 rpm idle and all 4 headlights on I got 13.65 v at horn relay and 13.88 at battery. Lights off and engine off 12.85 at battery.

All sealed beam halogens connected and voltage measured at terminals

Low beams only 12.75V at driver side and 12.65 at pass side

On high beams at pass side only 11.43V on the Hi Lo bulb and 11.38 V on the hi only. Didn't measure driver side as worst voltage drop will be at pass side.

Mad Electrical says a 10% drop in voltage will cause a 30% drop in light output. Looks like some relays will help.

Randy

TCracingCA

But I actually de-pinned the connectors and pinned them back up with larger diameter wiring for some applications. For the lights, I am running 24 Hour LeMans Racing H4's (Marchals) and I remember going to the junk yard and finding larger pinned mating connectors off of a large truck and using those to run the heavier gauge wiring. The junk yard is amazing place to find electrical components. If you think about our cars and the amount of wiring then vice now on these newer car, WOW!. The wiring in these new cars has so much more wiring, and some of the connectors that you can find are awesome for custom wiring projects.

But when I splice, it is clean----- I strip back one wire twice the length as the other, I twist the two together from the ends, but then fold the two twisted together back into the section of extra length stripped and then shrink wrap with a heat gun. Before folding I will flux the twist and the untwisted section and hit it with solder, and then fold and just touch the two together with heat to bond it all! Don't leave too much heat, or it will cause your insulation to melt back, which isn't good. If you do it right, it is hard to spot, especially if you use colored shrink. I hate to see the Yellow, Blue and Red connectors in any car or those with shrink over them! Looks like a snake that just ate something. I also in the junk yard like to look for neat looking clips for routing the wiring etc.. And it all costs next to nothing.

TCracingCA

You would measure voltage drops based on differing resistance etc..!! So how come you aren't focused on the important issue of AMPS?

DUB

THANK YOU---THANK YOU---THANK YOU

Kinda funny how that was mention in POST #2.

I have done this so many times....it is not a big deal but a lot to deal with to keep it safe and making sure that the relay is good enough.

I like using the GM relay part number 14089936. You can get this relay, connector, terminals and silicone rubber seals all from American Autowire.

This relay is for the cooling fans ...so handling 30 AMPs is no big deal...and I am sure your headlight will not draw that many amps. AND knowing that you will need to use 2 of these relays...one for low beam and one for high beam...these relays will last a long time and not be a problem....because the terminals in this relay for the power in and out are very large and have a lot more surface areas than many other relays I have seen....and they are water tight.

It does take a special crimping tool to attach the wire and seals....which I have....and you can get also....or make do with what you have....and tack a small amount of solder on the terminal if you are concerned.

DUB

Subfixer

So, here's the next question....

The C2 "Amp" gauge really measures the voltage difference between the junction at the horn relay and the battery. The gauge "calibration" is based on a known wire gauge/length/resistance between those 2 points.

More voltage at the battery vs the horn relay, caused by high amperage draw causing voltage drop at the horn relay, Amp gauge reads minus amps.
More voltage at the horn relay vs battery, due to alternator charging, then Amp gauge reads plus amps.

If the wire gauge between the battery and horn relay junction, as well as the alternator wire, was increased, what would be the effect on the "Amp" gauge readings?

Because there would be less of a voltage drop at the horn relay due to decreased wire resistance (larger wire, more surface area), I would think the "Amp" gauge would read less of an amperage draw than there actually was.

DUB

Your thoughts are correct...partially....BUT....remember this...the factory alternator is a XX amp one....so when I go in and install twin electric cooling fans...upgraded sound system and many other electrical components to bring the car more current with technology....I have to change the alternator to one that is more like current ones that have to provide a lot of power for so many components....and doing so.....I increase the wire side to mimic what GM does on the new Corvettes.

I have to look at my wiring diagram to see...because I can not remember all the wiring all the time....Because I deal in so many years and changes in wiring.

DUB

TCracingCA

Yes AMPS!

But PS-- you should know that I never read anything some of you guys write!

66RBS

I have not focused on amps for 2 reasons

1 I still plan on using my current Halogen sealed beams not H4 so amps will not change significantly.

2 The articles by Mad Electrical and Daniel Stern Lighting are focusing on reducing voltage drop by adding relays and taking most of the power load of the headlight switch, right?

The relays I am thinking of using are the 40/30 amp Bosch style with 14 Ga pigtails. 14 ga wiring from the relay to the headlights should reduce the voltage drop. Whatever the current draw is increasing to 14 ga from 18 ga and 16 ga seems to be a good move. Of course 14 ga wire will allow more amps but unless I increase the load ( change to H4) I don't think I have a concern.

I have a 61 amp alternator

As I said in my original post I want to take some of the load off the original harness. If amps are my primary concern I guess I missed the point of the relays.

Randy

BADBIRDCAGE

Randy: you may disagree with my running the 10 ga supply directly from the + bat terminal to a six fuse box to supply the headlight relays rather than from the horn relay buss to the relays but I was running a Painless harness and a 100 amp single wire alternator. I was also running relays for my headamp rollover motors as well as the headlamp circuits, my Vintage A/C and a second electric fuel pump for the TPI from that six fuse box.

Regardless of how you decide to do it relays are a good idea on the headlamp circuits.

TCracingCA

I see you aren't going for mega Wattage H4's, so the 14 gauge and your plan looks good for what you are installing. No need to get into technical.

DUB

And that is entirely up to you. But you are asking...and many of us know wrong really well also....and wanted to convey the importance of KNOWING this value. That is all

But knowing the value is something that I would want to know. But that is just me. REGARDLESS if I am increasing the wire size to 14 gauge.

CORRECT...using relays greatly reduces the load on the headlight switch and using the dimmer switch is what will be controlling your relays.

Using this BOSCH style relay in an area where water, dirt and moisture can get to the terminals...I would not do it. It will work for some time...but I also have to re-wire and configure some bogus wiring jobs on Corvettes where the 'test of time' is showing that where components were installed are beginning to fail...or the wrong type of component was used due to the conditions it is being exposed to.

If these BOSCH relays are in the interior...YES I WOULD...but out in the engine compartment...NO I WOULD NOT...which is why I mentioned the relays that I use that are water tight....and can carry the load. But do as you wish.

OK...here we go. Not knowing your car or having it in my shop where I can check the amp load on the system...I can not confirm or deny if the alternator will hold up. I have to guess that it would. I do many aftermarket upgrades and such and often times I have to change out alternators to later design ones that are much higher amp rating...such as 85 Amp and greater...due to the added electrical components that were added that are now requiring power that were not their from the factory. SO it all depends on what you have added and such.

Not wanting to cast any doubt...but it is a factor to consider. Much like some customers who installed a serious stereo system with a serious amp...and the alternator gets eaten up because it can not keep up with the requirements for the amp when used and wonder why they have to replace alternators often.

You can not 'take some of the load off'...when the load has to be there to make components work. You can do it another way that can make some components work better that originally designed. But the headlights are going to need what they need. But increasing the gauge size helps....and I am fairly confident of using 14 gauge is fine. AND YES...by installing these relays...if out in the engine compartment...you are actually reducing the amp load on the wires in your bulkhead/firewall connector that have the high/low beam wiring going through it.

The relays are saving the headlight switch and the current that goes through it will be greatly reduced because the power needed to pull the coil in the relay is so minute....versus the power needed to power up a headlight bulb (amps needed). That is why some of these aftermarket headlight switches will pop the internal circuit breaker inside because they are made so cheaply or on the 'razors edge' of working as designed....especially when halogen bulbs are installed. And this circuit breaker pops due to overload of AMPS...and as you know...a circuit breaker is rated in AMPS.

But why not pass along information that can help him or others....don't you agree.

DUB

66RBS

Dub,

Thanks for your suggestions and input particularly American Autowire. Viewed their online catalog and they have a lot of good stuff.

Randy

TCracingCA

Ok for alternator conversions, I recently put up a bunch of my helpful raw notes in a recent thread to help everyone with that. I even had pulley diameters to run things round and round, that spin the alternator!

Ok simpliest thing to do and no one here suggested it,, I know for sure because I actually read some other peoples posts for once, but mock up the relays and light to the existing looms just for testing and take some readings instead of just trusting someones specs or calculations. Put an amp meter or whatever reading you are thinking you want. There are wire gauge charts based on length of run that give amp loads. For a quick hookup of what you plan to run for a moment, it shouldn't hurt anything. But if you see smoke or something stop there immediately!

I also thought I gave a bunch of tips above. I probably have guys around the Country planning trips to the junk yards this weekend, guys buying soldering guns and heat shrink/heat guns, and throwing out yellow, blue, and red splices, lugs, etc.! all from one awesome post sharing! Smile thing here!

How is that! But you can call me out, because you come on and are helpful to people often. i see it!

Was that good enough?smile thing beer toast!