Alternator Conversion Question

F

fiftyv8

Senior Member
I have recently added a 6 volt positive earth alternator to my stock 29 Coupe.
I also installed a new battery.
Since I have done this conversion my amp meter continuously shows 10+ amps.
Is this right as I feel at some point the amp meter should be reading around zero when it is driven?

Any thoughts ideas or similar experiences that may help me out here.
 
It should drop back to near zero. Use a volt meter and read the voltage at the alternator output post and at the battery posts. I've seen a few alternators where the voltage regulator was bad and put out too much voltage.
 
It may never read zero, even with a 100% battery charge level. The root of the problem is the 10SI design 6V alternator conversion. There is only ONE 6V regulator currently available for the 45 year old Delco design alternators, and it has a whopping high 7.7V set point with NO time-taper and NO temperature compensation circuitry. TERRIBLE!

As a point of reference, there are a dozen or more 12V regulators for the Delco 10/12SI. The lowest has a 13.2V set, the highest, 14.8V. Your 7.7V on a 6V system is like having 15.4V constantly fed to a 12V battery. A 12V battery would cook to death in less than a year, boiling even in the winter if it had a 15.4V feed! Light bulbs will have the life of a popcorn kernel. Many original (Delco made in USA)10SI regulators were designed to start cold with 14.6V out, for about 20 minutes to recover the loss from starter cranking, then as the underhood temp came up, they went down to about 13.2V. The 6V regs stay high, no temperature compensation circuitry.

Now add to the problem the peanut size (2" diameter) pulleys sold with the 6V perversion alternators. You have the full 7.7V output even while idling! Generators never charged at idle. I remember my mom's '51 Buick and all of grandpa K's Caddys. Everybody's "GEN" dash lamp glowed a little at idle. Your amp gauge often showed discharge 'till 10 mph. The repair manuals for old external 3 section 6V regulators (those big rectangle black boxes on the firewall) spec'ed either 7.10 or 7.15V as the set point, + or - 0.05V. Later, the 12V genny's were spec'ed at 14.25V. I repaired and adjusted plenty on a Sun generator test bench.

So why are the 6V regulators set so brutally high? To make the dumbass general public happy. 99% of all 6V vehicles are occasional use only. When you start them up, the battery is likely 1/3 or more down, and they are driven only an hour or less. The wiring to their lights is long and rotten, causing loss. They (the dumbass public) thinks an alternator is only 'good' if your lights get way brighter with the motor running, even if the battery is 100% and it's 100F outside.

The REAL answer is a 7.2V regulator set point for people who drive regularly and often at night with halogens and good wiring. This is possible, but would require either modifing (tricking) the existing regulator with a zener and a few other components, way beyond the skill level of most, or making a new limited market regulator that would be way too expensive to compete with the junk that is now sold. The only other fix for you is to (gasp!) go to 12V so you can run an alternator that has proper voltage set and control for daily driving. I have two A's- My 40B is original generator, my 160B is 12V with a denso alternator that is NOT a one-wire conversion P.O.S.
 
You could feed the alternator output through a diode and drop it 1/2 a volt----- or replace the troublesome alternator with a generator
 
Mike, yep.

If you live Alaska 7.7V is good. Make that 15.4V if 12V.
If you are driving like most Model A owners you might just go with it. It's those long trips that can make the battery gas, if it does.
Temp compensation would be nice. Transpo does not list if it is or isn't.
 
I am starting to wonder why I ever decided to go with a 6 volt alternator.
Would a bigger pulley help?
Where exactly does the diode need to be located?
 
I have had a positive ground 6-volt alternator on my Vic for over 20 years. When the battery is fully charged the ammeter needle always returns to Zero. If it does not it could be an indication that the battery is not fully charging up due to a defect in one of the cells. Even though you installed a new battery, it could still have a defective cell.

Tom Endy
 
fiftyv8 said:
I have recently added a 6 volt positive earth alternator to my stock 29 Coupe.
I also installed a new battery.
Since I have done this conversion my amp meter continuously shows 10+ amps.
Is this right as I feel at some point the amp meter should be reading around zero when it is driven?

Any thoughts ideas or similar experiences that may help me out here.
Click to expand...

Have you run it long enough to fully charge the battery? When the battery is fully charged it should cut back to just a few amps but not to zero. The regulator is designed to reduce the output to a minimum but not to zero.
Bill
 
As Kurt in NJ mentioned, a down and dirty fix would be to run your alternator output wire to a 100 amp power diode on a giant heat sink. That would knock you down from 7.7 to a correct 7.1 volts irrespective of amperage load. Again, not a simple "kit". @ 50A it would need to dissipate 30 watts of heat. (P=VA, V=0.6, the silicon junction drop) Here's a 100A silicon diode with sink, about $35 on ebay. You would also need to electrically isolate the heat sink from any vehicle metal when mounting. Kinda big, clumsy, and ugly.
$T2eC16RHJGwE9n)yTU2pBQ(jcrPCjg~~60_12.jpg


There IS a different (non-10/12SI design) 6V one-wire alternator you can get that is based on a much later 122CS alternator design with (geek alert!) an AC not DC regulator for low speed turn-on, a more livable 7.35V regulator set point, and some temp comp. I see them on eBay occasionally.
KGrHqFHJBEE-byTWv-yBPnuKcdlw60_12.jpg

Personally, the whole generator vs. alternator issue confuses me in how Model A people react to it. You have one camp that wants 6V and doesn't mind the non-stock alternator look. Then you have the other camp that demands that generator look, but doesn't care if it is 12V (genern ator, $600 :eek:) so they can run all kinds of high wattage demand stuff.
 
fiftyv8 said:
I am starting to wonder why I ever decided to go with a 6 volt alternator.
Would a bigger pulley help?
Where exactly does the diode need to be located?
Click to expand...

I was wondering why you did, too. :D

I think most people do it for the voltage regulator that is built in, instead of having the constant charge rate of a stock generator (which is not enough some times, and too much other times). In theory, the voltage regulator in the alternator would do it, but as you see here, it's not really a very good one.

Staying with a properly working 6V generator with a hidden electronic voltage regulator is a better way to get the current you need when you need it and not boil your battery. Plus it looks so much better than an alternator...
 
I also do not understand all the fuss over using a 6v alternator. Like Tom Endy, I have had one for about 8 years now, and it works perfectly. After I start it, it charges at a modest amount for about 5-10 minutes, then drops to zero, where it stays. I have never added anything to it or had it modified in any way, and my 6v batteries last just fine. I run quartz halogen headlights and am very happy with the setup, even though I keep hearing alternators don't work, don't last long, have to tighten the pulley too much, and generally just bad news; makes me wonder what I did wrong to miss out on all those issues!
 
I run a 1935 Chevy truck Delco-Remy (946C) generator on my '31 roadster. It puts out more "juice" then the stock "A" Ford genny.;)
At least that is what it says on the '30s/'40s adapter bracket box.:eek:

Bob-A:D
 
I should add to the discussion that many years ago there were at least three different 6V 10SI regulators. One was 7.25V set with typical 3-wire remote sense, excitation, and idiot light config, one was a "B" circuit regulator, one 7.4V set with internal excitation and no spade tabs, and the present "too hot" 7.7V version from transpo.

If you have an older 6V 10SI 6V alternator you may not have the issues associated with the present regulator.
 
I chose the expensive route, and it is quite. Satisfactory. If I had the skills, a electronic regulator conversion inside a stock generator would have the VERY BEST achievable solution (in my opinion).
 

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Tom Wesenberg said:
It should drop back to near zero. Use a volt meter and read the voltage at the alternator output post and at the battery posts. I've seen a few alternators where the voltage regulator was bad and put out too much voltage.
Click to expand...

In years past at least 2 of the alternators I bought for Model A's were putting out around 8 volts and didn't cut back. After replacing with another one (Nu Rex) they cut back perfectly to just over 6 volts, one of those old alternators killed the battery in one night if I didn't disconnect it so it makes one wonder if these things are tested before shipping. My present alternator that been in my coupe for 20 years (Nu Rex) works fine.
 
Hi Fifty,

Appears adding modern Model A appurtenances sometimes adds confusion and unwanted future problems while trying to enjoy a nice "stock", 80+ year old Model A like yours.

E.g., ........... if one has a healthy head of hair at 80 years old ...... why keep trying on different unnatural looking wigs & hair styles that look completely out of place.

In comparing aesthetic opinions of many Model A owners, "stock" 6V generators often look better and usually work great.

And, unfortunately ........... most people who recommend using Model A generators are usually people who sound just like old people ...... and really, after time, some of us don't care if we are thought of as old people ...... just one old opinion ..... and best of luck with your project.
 
I agree with TerryH about not having a problem with an alternator. Installed a used Nu Rex 6v. pos. ground alt. 4 years ago on my 29 Tudor. I have owned the car 5 yrs. and have no idea how old the battery is but it starts and runs fine. It is usually driven daily all summer long.
 
Thanks every one for your thoughts.
From this I will contact my alternator seller and see what he has to offer as a compromise.
Currently, I am happy with the way it is working but concerned that it may cook the battery eventually.
After running both the generator and now the alternator, I am figuring that maybe my amp meter could be reading a little high since with the generator the setting for a trickle charge was never enough although it read OK and now with the alternator it reads 10+ and that is scaring me.
I don't drive the car regularly and saw installing the alternator as the best way to achieve battery recharge when I did use it.
Its the same old story, one modification seems to lead to another...
 
Just a crazy thought here. Have you measured the output with a different meter?
Don't get me wrong. I'm the last guy you'll meet who blames the tool, but if is as old as the rest of the car, its accuracy is suspect.
 
Yeah, good point I will get that checked.
Better check the easier and less costly stuff first...
 
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