Technical Alternator Conversion SBC

Hey guys! I've been running the roads all things peachy put 1000 miles on the small block since last I posted thanks to everyone who helped out with my shifting issues! So my alternator went South on me driving back from Houston my last trip down there... I ran fine but my gauge was reading around 11 volts and I have a meter that plugs into my cigarette lighter that was reading 11.3 volts and at night with brakes applied around 10.9 so desperate and far from home I unplugged the blue and black wire plug from the alt and it over charged to 16 volts and I plugged it right back in!
It shocked me that the car didn't die but everything was okay. So I got back home and I put a replacement alternator in the car but suspecting that maybe the regular had failed I bought one with an internal regulator and jumped the plug that went into the fire wall regulator like I had seen online In the conversion. It worked for a while charging at 14.2-13.9 at idle then all of a sudden after a test ride it was back down to 11.5... confused I put my volt meter on the lug on back of the alternator and it says 11.5 volts at idle same as on gauge... What did I get wrong here? Also it's worth mentioning I bought a reman alternator from parts store around the corner was all they had but it was the cheapest in the store remanufactured in Mexico valucraft...so maybe it's a dud? Any help is greatly appreciated

 

The current setup

 

sounds like you originally had an external regulated alternator ,and you replaced it with an internal regulated one. you may not have it wired correctly............ where are those black and blue wires going to? what's with those jumper wires? it's time to do it right. i have wired dozens of cars and never had a charging issue

 

The black and blue wires go to the dash battery indicator and to the ignition switch according to my shop manual and it was externally regulated now its a si alternator for '75-81 Chevy cars and I found the conversion instructions a few different places and they all said to jump the plug to the regulator as I had pictured... However I'm ready to do it right so whatever guidance I'd be grateful, so what's with the alternator only making 11.5 volts how can something hooked up wrong effect the output of the alternator? Thanks for the response!

 

That’s an internal reg 10si alt, you need to re wire it. First they make a connector for the alt so there’s no arching (which it looks like it hit the case already) and it’s only a few bucks.

Or if you start fresh:



Connector:

 

Okay I ordered a plug it'll be here tomorrow and I'll be ready to restart from the beginning to get this correct... The alternator is putting out 11.5 I removed the hot battery cable and instantly the engine dies so I know the alternator is toast? The question is did I somehow burn up the internal regulator by having it hooked incorrectly(arching?) And when you say start fresh I can run a new wire from the battery to alternator and then to ign switch? Would this be advisable? Also is my jumper set up incorrectly executed? By the looks of the diagram I need to just jump the two terminals on the alternator to self excite? How can I make it like a stock '78 and later internally regulated set up? Thanks again!

 

If I "start fresh" can I just get rid of every old wire that has to do with the external regulator and just run an inline fused wire to the ignition switch and battery?

 

Very simple solution is to use a single wire alternator. Just run a #8 or #10 wire from the alternator to the pos battery terminal. Best to use an inline fuse or purchase a fusible link wire at the parts store.

 

Is your 1 2 terminal connection's correct? If backwards it won't excite correctly. Do you have a dash (gen) light in your car? If not no exciting or start up of charging system will happen unless you rev the piss out of it.

 

I’ve done it both ways, new wires and existing wires (just bypass the regulator). If you want to run new wires for the alt then run a 10g wire from the battery + (you can either use a in line fuse or fusible link), to the 12v lug on the back. With your new connector plugged in, run the #2 wire to the back 12v lug on the alt and the #1 wire goes to the dash warning light. I would try the alternator you have first and unplugging the battery while running isn’t a good test.....use a volt meter (amp meter is the best) or take it in to be tested.

I personally don’t like 1 wire alts, I like the idea of a warning light.

 

You just have wires left and unless there's on that's broken why rewire. Test test test. Replacing things without confirmation is a waste of time and money.

 

What the video said^^^^^^ easiest way, couldn't have explained it better, although I'd have tried. 10 si alternators are incredibly simple and reliable, no need to go to a one wire, plus.....try finding a one wire in bumfuck nowhere after dark, where 10 si alternators live on farmers scrap cars. Remember that.

 

1 wire or 3 wire is like a Holley vs Carter carb debate. That fact is a 3 wire system does a way better job of charging and controlling it . But, there are those that prefer the easy way of doing things so 1 wire is why it's popular.

 

Use the 3-wire configuration. You get to retain a warning/idiot light and the sense lead will insure that the charging voltage at the battery is correct.

 

I use the 3-wire method, tried and true and no wires left over that don't have a home. I generally use a 63 amp 1974-ish Chevy alternator, I can get one anywhere and probably have a core or two at home.

 

That's an extremely good point... So I've got another 10si alternator its a new Wilson unit 63 amps for a 1975ish chevy. I got the plug also to avoid the arching that was mentioned before, I've got 10 gauge wire and I also got a 60 amp fuse which brings me to my next question...does an alternator make that 63 amps all the time just at start up? Or is it capable of putting out 63 if the current draw was that great? And for 1oldtimer I appreciate the walk though on the rewire..is there any advantage of an inline fuse to a fusable link or vise versa? Thanks to everyone for chiming in! Tomorrow I'm going to do this rewire and I'll report back

 

No. Voltage is applied. Current is drawn. So consequently the alternator will only supply the current that is required. Keep in mind though too, an alternator that is rated at say, 70 amps should not be loaded down at 70 amps on a continuous basis. They should be derated somewhat. Also small amounts of corrosion, even invisible, at ground points and cable connections &c, anywhere in the circuit or ground path, will cripple the current output. Grind down to clean bright metal. It is very important that the alternator itself too, has a clean and tight low resistance connection through to the mounting block and brackets (no paint); that the cables aren't corroded, battery terminals shiny bright and tight. It pays to do this and doesn't cost anything other than time.

 

Chevy Guy, The only way to check the regulator, aside from taking it down to the 'Zone, is to first wire it correctly, without all the bypasses and jumpers. Then look in the back of the alt. for a little D shaped hole. Inside, you will see a little metal tab. You want to ground that tab to the case with the engine running. You will be full fielding the armature, creating max voltage. If you get 14-15 v, then yes the regulator is bad. You can replace it, by itself. Read up on how to retain the brushes and have at it, Mr Chevy.

 

Thanks for the info on that I'll make sure that I clean every connection while I'm hooking it back up..Haha hey Mark! Thanks for the tip I'll definitely check it once it all put together (correctly this time) and I'd be interested in trying to service my alternators I'll do some research on that!

 

Okay so I have everything hooked up grounds are sanded the plug is installed on the alternator and the number 2 terminal is jumped to the 12v feed on rear of alternator, the factory 10ga wire is also connected there the old blue wire is left loose and the white wire is connected to the idiot light. I have the old regulator removed and I have jumped the terminals on the plug just as shown in the video. Am I supposed to have a wire from the alternator directly to the battery positive in addition to the 10ga factory wire going to the bulkhead?right now I have no wire going directly to the battery from the alternator....am I missing anything before I test this? Thanks guys!

 

In future for anyone converting from External to Internal regulated Alts and you don't want to cut into your original harness...
https://www.lectriclimited.com/conv...fications/alternator-conversion-harness-84950
They also have kits to use the later CS alternators as well.
Summit sells the Ameriacn Autowire kit 27555 for SI Alt conversions.

 

Doesn't have to come straight from the battery, but yes, you're supposed to have a live 12 v wire on the main terminal. That's why they put a red cap over it.

 

Thanks and thanks for everyone's input on this it was a success and it's now charging 14.1 volts!

 

Yeah Baby!

 

I'm not crazy about the white wire, the splice looks lumpy, but still may be okay. I would at least sleeve it with something. Also the wiring needs to be better-supported. But you managed to solve the main problem!

 

It's all going into some conduit as well as the harness...and I will open the white wire back up... I did get a good bit of soder on the wire. Thanks again everybody!

 

Just when I think evreveryth is golden I go out to start the car and it's dead... I start hunting around looking for shorts and the alternator is hot to the touch...car hasn't ran today at all it has me confused to all hell....does anyone know what's happening here????

 

Charge it up. Disconnect and check the no. 1 terminal with test light or v/m , key off. Should be nothing there. If there is , it's wired wrong.

 

Okay thanks Mark I'm checking it now

 

Number one terminal has 12.4 volts key off

Number one terminal has 12.4 volts key off and with the plug unhooked from alternator. What did I do wrong here the number one is connected to the black and white stripe wire going to dash