Wire size concern when updating Alternator

[Logan Robb]

Good evening all!

I am in the process of diagnosing more electrical gremlins in my 64 Fleetwood. As part of this, I am thinking I should replace the alternator and regulator just to have a fresh start there as both are original. 

I've read over the article in the "Help" section about alternator upgrades and I think I will take a similar route but stick with a 10DN alt and external regulator. The main reason for this is my concern with upgrading to a 12SI style means the alt can output many more amps that the alternator that is stock. I would like to leave my stock wiring the way that it is and not have to fish new, heavier gauge cables. 

I think there is a bit of a knowledge gap as well-if the alt is rated for 150amp, does that mean it is always sending that amperage out? Or only when needed?

I have added nothing more to my 64 that would draw more amperage, but I do like the idea of having the extra amps available in the future should I change something. I just want to make sure if I put a "larger" alt in, I wont burn my car to the ground. 

Further, I should replace the voltage regulator too should I maintain the 10DN style. Any good recommendations for a quality part?

Thanks again all and happy cruising!

Logan  

[a5c0048011b941599a2e58cc24e9eb2f]

I'm not an electrician, and I'm sure there are others on here with more electrical knowledge than I have, but I've owned and restored or modified about 50 classic American cars of my own (1957-71model years) over the past 45+ years. 

My advice: Unless you are wanting to install a mega-watt sound system and other high amperage draw devices, it's best to keep the system as close to stock as possible.

The wiring in these cars was not meant to carry much more than the stock equipment, back when in the best of condition.  Pile on six decades of wear and tear, and the wiring most probably will be weaker than when new.

We also need to factor in the unknown work of previous owners, such as haphazardly splicing-in stereos or ignition cut-off switches with mere electrical tape connections, crimp connectors, or improper cold solder joints that are working themselves loose.  It doesn't take many failing splices or over-heated connectors to burn a car to the ground. 

If it were my car, I'd rebuild the stock alternator and voltage regulator to equal the stock specs of the highest output Cadillac alternator for our generation of car. Did the limos with A/C get the heaviest-duty alternators? Upgrading to that spec might be the smartest way to increase output without going beyond the designed capacity. 

If you want brighter lights inside and out, LEDs are a good choice. Those would effectively lower the strain on the electrical system too.

Question for the forum:  Does any company make high-quality engine compartment and dashboard harnesses for our cars?  If there is (and if you feel like getting into a project that big) then it would be smart to install those harnesses before cranking up the alternator output or adding any hefty electrical system loads.

I realize that your post said that you aren't planning on adding any heavy-amp-draw items.

This is just my "I really hate electrical fires" viewpoint.  Good luck and let us know what you choose to do. 

[Logan Robb]

I would agree! I really hate electrical fires as well, especially on my own car!

My gut reaction is that the system only draws what the system needs from the alt-So keeping everything stock like I have it wiring and component wise but putting in a slightly larger output Alt shouldn't try and shove any more amperage thru the wire. But I am not an electrician either so I figured I should confirm with the group FIRST. 

As for the work done by others, it really seems as I have the car longer and longer, it doesn't look like there were really any hack jobs with their hands in my car. I am probably the biggest hack job that HAS touched it. 

I will certainly keep this thread updated. Thanks for the reply!

Logan

[Logan Robb]

What was the amperage of the original?

[Logan Robb]

I took my hour lunch break today to research this issue further and have found it to be a simple answer. Supply and Demand. Alternators with enough Supply will give whatever the electrical system demands. If the Alt cant Supply the Demand, you'll drain the battery. So what this means is being that my car is "stock" in the way of there being no major electrical modifications, the larger Alt, tho capable of Supplying more amps, will only give what is demanded of it. 

Short answer, you can never have "too much" alternator. 

So perhaps an upgrade to the larger alternator is a good idea. I can see no negatives. Larger alt means less work to charge the battery and more efficient overall. 

Will let you know my install process and go from there. 

Logan. 

[Kurt]

The stock alternator for a non-AC car is 42 amps. For an A/C car, 52 amps. All true what you said above. The alternator will provide the power needed to charge the battery up to it's max output. I replaced my alternator with an internally regulated 100 amp unit about 5 years ago and have had no issues at all. I have an aftermaket stereo & an electric pusher fan to assist cooling the A/C condenser, nothing crazy power hungry.

If you do go with an externally regualted setup, get a good solid-state unit. The original mechanical voltage regulators are problematic as they age.

[a5c0048011b941599a2e58cc24e9eb2f]

Ok, I learned something. Good to know. Thanks. 

I typically err on the side of safety. Especially after seeing in person a beautiful 1970 Dodge Charger's wiring catch on fire and consume the car shortly thereafter. The culprit was a bad factory harness.    

I'd still recommend to keep an eye on the wiring system after you upgrade the alternator. IF your battery is low and NEEDS more amperage, your NEW ALTERNATOR will send more amps through the system than before...and that could possibly cause a problem with our old wiring.  

But, since you're not installing a head-banging stereo or a modern airbag suspension, I'd agree that all should be okay. 

I repeat: "I really hate electrical fires."
 

[Logan Robb]

I don't think I would go anything over 100 amp. Just something with more juice if I add a pusher fan which is also something I have been considering. 

With my new found info, I may go for an internally regulated alt following the "Help" section guide to maintain the Gen light (which my bulb is apparently burned out because I learned that my alt is dead thru other means). That cleans up the wiring in the engine a little and make rooms for something in the future in that space. I am thinking of adding a coolant recovery tank and that looks like a swell spot for it. 

Thanks again, always nice to have access to the wealth of info here!

Logan

[a5c0048011b941599a2e58cc24e9eb2f]

Sounds good. Post a few pix along the way.

[Jason Edge]

Just to add, 1964 AC equipped alternators were upgraded to 55 amps. Amp hr rating of the batteries went from 70 to 73. Both not significant jumps but it did increase a tad.

[Logan Robb]

Yes, I noticed mine was a 55A alt when looking at it, so mustn't be the original

[Jason Edge]

Logan, Assuming your 1964 Fleetwood 60 Special has AC (most do), 55 amp would be correct for your car.