Hello All,

Recently switched to the 10/12SI alternator variety on my 350 Rocket.

I have the diagram that Joe P provided some years ago that shows the proper wiring, I believe to have done this correctly.

Friend of mine was junking an 83' firebird so i pulled the new alternator off and am using that. Bought the proper pigtail connectors and i was off to the races.

Here is the issue. When i initially cold-start the car, the battery voltage is at 11.5 to 12.0V.

If i rev the engine to exactly 1500RPM, all of a sudden, the alternator kicks in and starts charging, and works great for the rest of my voyage.

Why do i need to rev the engine to get the alternator charging??

THANKS!

-Tony

 

I dont really know which type of alternator it is... all i know is that i ripped it off an '83 Firebird that had a V6 two point something litre engine...

I think it's this one.

ACDELCO Part # 3342113 {#19135671} Remanufactured; 63 Amp
GENERATOR 2 DOORS; DELCO 10SI 63 AMPS; w/o A/C MAN CONT(C60)

What is the difference between 10 and 12 SI??

Also, i found "ALTERNATOR/GENERATOR RESISTOR" on Rockauto. Is that what you mean might need to be replaced? It's less than a dollar.

STANDARD MOTOR PRODUCTS Part # RU25 {#830478} Blade Terminals; Terminal Gender: Male; Direct OE Replacement; Number of Terminals: 2; Mounting Bracket: Yes

 

Also, is it possible that the alternator in the firebird was Physically spinning faster than my olds? Maybe 1500 RPM in my Olds is equal to whatever the firebird was geared to idle at with its pulleys..

 

The difference between a 10 and 12 SI is 2. Just kidding. They are the same basic alternator, just a slightly different design. The biggest difference electrically is the windings and rectifier. 12 SI have a better low rpm performance and some are of higher amperage.

The need to rev to 1500 may be there is a 1 wire reg in it or the alt was rebuilt with mismatched parts.

 

The way i currently have the alternator wired is as follows.

The big red terminal goes to the same place that the old alternator went to.

So, looking at the above diagram, i found that the white wire (Terminal 2) really just connects to the red, which connects to the horn block.

So at the Moment, Terminal 2 is connected directly to the horn block, and so is the big + BAT Terminal.

Did i wire this wrong maybe?

 

Actually, here is a picture which clearly shows what is connected and what is not and how i wired it.

 

Looks like it's operating as a single wire alternator which will behave as described.

 

If you don't have the wire connected from the #1 terminal to the brown wire going to the GEN light then 1) you DIDN'T wire it the way I showed you and 2) THAT's why is isn't charging at low RPM. The SI family alternators require the signal from the idiot light (or a 35 ohm resistor) to turn on the regulator at low RPMs.

 

Great! Thanks,

I will cut the wires and splice them in properly this evening and report my findings.

( I was trying to avoid cutting the wires so the firewall would look as authentic as possible...)

 

Yep. Without the lite wire it will act like a 1 wire.

 

GREAT NEWS!

Cut the brown wire from the old voltage regulator and spliced it directly to the terminal on the alternator connector.

BOOM, fired up the cutlass, Alternator Automatically jumped to 13.5V, no need to rev.

Thanks for all the help. Amazing what one wire will make a difference.

 

Just to confirm, I wired up my 10SI the way Joe shows above and it works well. My understanding is you want the #2 sense wire far enough away from the alternator to give it a good read on the voltage in the system, so the alternator knows whether to raise or lower the votage output. I confirmed this by looking at the '75 Chassis Service Manual which shows the #2 wire being terminated at the junction block. As Joe shows, the #1 wire goes to the Gen light.

In my '66 big cars there are two wires to jump the #1 field wire to: a brown one going to the Gen light and a brown/white single strand. I used a brown wire from the alt to both, soldered it up and it seems to be working as intended.