Delco 10si - Testing??

Is there a quick and easy way (other than take it to my flaps) to test alt output on the vehicle? Have the 10si (3 wire) on the '56, shows no output on the ammeter. Always had to do the throttle blip to get it to charge. Battery is now low due to lack of charging. Has been fine until recently. Went to start a week or so ago and had to jump it. No obvious shorts, all fuses good. Where do I poke it to check it?

 

What is the voltage at the "Bat" terminal at the back of the alternator when the engine is running?

What is the voltage at terminals #1 and #2 when the engine is running?


Does your wiring look something like this?

 

"Where do I poke it to check it? " From terminal to ground, or??

 

WAY easy test........put a DC voltmeter (multimeter on DC volts) across your battery terminals. With the eninge running, and all/any accessories turned on (heater blower, headlights, flashers, etc.) the voltage should be 12.75 (13) Volts to about 15 volts. If you need to rev up engine to obtain see below.

If you are reading below that, check your belt for tightness and/or glazing. If you can spin the alternator by hand (engine NOT running) with the belt engaging the pulley, the belt is too loose or too glazed or wrong belt. Could also be regulator, but not as common.

If you are charging TOO high of voltage, your regulator is shot. Replace.

 

Set the voltmeter to "DC", if there's a range, set it to the range just above 12 volts. Put the black lead to ground (chassis, or the negative side of the battery). Put the red lead to the "Bat" terminal on the alternator (or as BC3Jeep says, you can go to the "+" on the battery to get an idea of what is going on).

 

Yes, terminal to ground.

Also, it might be useful to measure terminal #1 with the key on but the engine not running. There should be a voltage present on this terminal to provide the magnetic field to get the alternator "started". Once it's generating power, it will self-energize to maintain this field.

The fact that you had to "blip" the engine suggests that either terminal #1 is miswired or something's wrong inside the alternator. If you see a voltage here with the key on and without the engine running, it's probably the latter.

 

Wire from "Batt" terminal goes to ammeter. Return's from ammeter back to batt +. I have a wire Jumpered off ammeter to fuse block for main harness power. #2 terminal spliced into "batt" return wire from ammeter. ( I think, it's wrapped up in a loom). #1 wire goes dash cluster amp light. Battery is trickle charging overnight. Will start up in AM (gonna be around 5-10* above 0) and check output.

 

On the back of the 10SI there should be a small half moon hole just off the rear bearing part of the housing. Looking into the hole, you should see a metal tab that is attached to the internal regulator. It will cover the hole from the inside. This is the test grounding tab for the regulator. With the engine running at about 1K to 15 hundred with a fully charged battery, you can ground this tab with a small screwdriver to the case. Your volt meter should jump to about 15 volts. Don't leave it there long, just enough to see your voltage jump. This tells you the alternator is good but the regulator or some of the wiring is bad.

 

great thread, i am planning this job with a Delco SI knock off, I am confused about this "option" of having an alternator that does not kick on til you rev the engine real good? What is that about?

 

This wiring sounds reasonable, assuming it's intact. When you turn on the key, does the "AMP" light turn on? It should, then it should go out when the alternator starts generating. If this light doesn't ever come on, the bulb might be bad. Check that the other side of the "AMP" light is connected to switched 12V (either the ACC or IGN terminals on the ignition switch, presumably). With the key on, but the engine not running, ground terminal #1 and see if the "AMP" light comes on. It should.

 

In a 3-wire SI alternator, terminal #1 supplies current to the alternator's field coil to produce a good magnetic field to enable the alternator to start generating electricity at lower RPM's. Once it is generating, the alternator maintains the field using some of the generated power. If the startup current is not present, you can usually get the alternator to "start" by running it at higher RPM's. Residual magnetism in the field core is enough to get the process rolling if you rev it high enough.

Some people like to use "1-wire" alternators, which rely completely on the residual magnetism. A proper 1-wire alternator will contain different parts which will allow the alternator to start up at somewhat lower RPM's, but you still need to get the RPM's up a bit to get it going. There are other 1-wire schemes, but frankly I miss the point of all this -- to me, the 3-wire advantages far outweigh any disadvantages of the "extra" 2 wires.

 

OK so did I buy a one wire or three wire????

See photos here! The shots of alternaotr are about 15 shots into my album, enjoy the ahow shots and others along the way!

http://s557.photobucket.com/albums/ss14/mwinks-jeep/

 

Looks like 3-wire to me. If you're having problems with it, you'll probably want to fire up a fresh thread to discuss it further.

 

Found out mine was kaput. Was about 4 years old, but not a huge amount of time on it. Noticed that almost every alt swap pic I see has an alt like mine (typical Delco 10si). Did you ever notice that the fan is backwards for an f-head swap?? I know the alt doesn't care which way it turns, but the typical GM application has the alt on the drivers side of the motor. When you put the alt on an f-head, the alt fan is actually backwards. Think that would contribute to an early demise, as the cooling air may not be sufficient??

 

I wondered about this myself as I was dozing off last night, just got the alt in and thought...that thing is turning the wrong direction.....I will see if that truly is the case on mine...

 

I guess it would have to if you actually put a belt on it now wouldn't it.

 

One of the best pics I have seen for a delco. Thanks for posting.

 

Plus an alternator doesn't care which direction it turns.

<oops - read the earlier post>

Yes, the fan function would be different.

 

But it is not a question of engine direction it is a question of which way the cooling fins are scooping. If the scoop at 12:00 is pointing left and the alt rotates clockwise the scoop is not scooping. If it turns counterclockwise it IS scooping. That is the concern, right? I did not look at mine yet, as wiring on my new job is not sufficient so right now it ain't going nowhere.