Technical Totally frustrated...need Delco 10si Alternator help

Running a 12 volt Delco 10si conversion on my flathead. Tried 2 different replacement alternators, and can't get the warning light to go out when the motor is running. I run a voltage gauge and a warning light. The warning light is hooked up to terminal 1 on the top of the alternator. Power to the warning light is supplied from the adjacent Gas gauge.

Terminal 2 is jumped to the B+ wire, which is hooked to the hot side of my Ford solenoid switch. Terminal 2 is hot all the time. Engine fires like a champ, battery is new.

Terminal 1 is NOT hot when the motor is off, and gets very little current with the motor running (less than one volt).

In order to make the warning light go off when the motor is running, shouldn't terminal 1 be making 12 volts??? As I understand, that with the motor running the warning light would get 12 volts from both Terminal 1 and the battery side, no current would flow, and the light would turn off. The warning light dles go ON in the keyed position, but fails to go out when the motor is switched on and the alternator is making power.

With the motor running, I can put my voltage meter and jump from Terminal 1 and ground to the case, and I am getting a very low voltage reading- again, less than 1 volt.

Do I have the correct alternator from the parts store? It is from a 1978 Camaro with 350, as per the instructions from this article.

http://www.madelectrical.com/electricaltech/delcoremy.shtml

Very frustrating, and insight you might lend is much appreciated. Thanks in advance.

 

http://www.oldengine.org/unfaq/10si.htm

 

Chevy put a resistor wire in series with the light, give that a try? I don't know what the specs are, but it should be around 10 ohms? try a 1/2 watt, see if it works.

http://www.radioshack.com/product/i...62309&filterName=Brand&filterValue=RadioShack

 

I think I have this thing figured out. I believe it is the pulley size. See photo below:



Stock pulley on left, 4 5/8ths. Pulley on right is off the 10si alternator, 2 1/8th.

The fellow who did the conversion wanted to retain the stock fan, which mounts to the front of the pulley. But the Delco pulley is too narrow for the flathead belt that also runs the waterpumps. So he had one made to fit the flathead belts, the Delco shaft and mount the stock fan. But he had it made the same big diameter as the stock generator pulley, rather than the size that now comes on the Delco alternators.

He didn't realize that the diameter was too large for the alternator, and wouldn't spin it fast enough.

As a result, the alternator isn't turning enough to produce the juice it needs. With the motor on and engine at idle, the voltage is 12.4 across the two battery posts. Needs to be higher. The alternator hasn't reached enough rpms to kick in and produce current.

Does that sound like a reasonable explanation? Does the Delco unit need to turn a certain speed to make power?

I noticed in the Speedway catalog there is the correct pulley for this conversion. Here is the reference;

http://www.speedwaymotors.com/Flathead-Alternator-Pulley-with-Fan-Mount,8946.html

Please let me know if I'm onto the right track here. Thanks.

 

if you rev the engine to 2000 rpm, then the light should go out, even with a huge pulley on the alternator

 

I revved the motor, but don't have a tach so I don't know how high. Probably not 2000rpm. The pulley is underdriving the alternator by more than 50%. Is it true that the Delco units are switched so that if the shaft isn't turning fast enough the alternator will only make minimum power?

 

Jim, yes, I am told that the warning light circuit must be used in order for the alternator to operate correctly. I have never wired in a resistor wire. Does that piece from Radio Shack get mounted in a holder of some kind? You'll have to parden me, I'm ignorant here, know just enough about auto electric to regularly shock myself. Character builder.

 

Just found this article. Terrific. I have some rewiring to do.

http://www.junkyardgenius.com/charging/delco01.html

 

A diode might do the trick too, I have one in one of my cars, works fine.

The resistor or diode doesn't need a holder, you cut the wire and solder the ends of it to the ends of the wire, and tape it up or put heat shrink tubing over it.

 

It sounds like you have it wired correctly. Terminal 1 should measure 12 volts when the alternator is charging, which will, as you said in your original post, cause the alternator light to go out, since it has 12 volts on both sides of the filament.

You will have to rev it a bit to get it to start charging, but once it does it will continue to do so, even when the revs drop back down to idle. You'll have to rev it each time you start the car. I have a 10SI on a John Deere Model B, and have to do this each time to get the alternator to excite. Rev a John Deere Model B, borders on an oxymoron.

The Speedway pulley isn't much smaller than the stock genny one, not sure that will solve your problem.
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Regarding the link in post #8 above, the directions calling for the #2 terminal to be hooked to the horn relay because "The Horn Relay is at the end of the wiring harness, and will have some of the lowest voltage in the system so the alternator knows to add more voltage" is wrong on a couple of points. A.) You do not want to have the sense lead (terminal #2) connected to a "lowest voltage" point in the system and B.) the horn relay voltage will be a pretty good reference point since it is normally connected into the harness with numerically low gauge wire, thereby having minimal voltage drop. Terminal 2 is the voltage sense lead, and was designed by Delco to be connected to a point as close to the battery terminal as possible, as that voltage is the "reference" it uses for regulation of the alternator output. Connecting terminal 2 to a "low voltage" point in the system will cause the alternator to put out higher voltage than is required to charge the battery, and could result in cooking the battery or other electrical devices.

The only advantage to using a low voltage reference point is that your lights will be brighter.......

 

So what should I connect my #2 terminal that is hot all the time? Other than the horn relay, what other alternatives do I have? How about to the hot side of the ignition? A better alternative?

Again, fellas, thanks for your help here.

 

The horn relay is fine. I was just pointing out that the horn relay is NOT a low voltage point at the end of the wiring harness, like the article says it is. I always run mine directly to the battery post.

 

They do make a normal diameter wide belt pulley for a Delco alternator, we used to pick them up from the local rebuilder when we did alternator conversions to older equipment.

Your system should work if it is actually wired as you described, when the alternator is charging the current from the #1 terminal and the light should balance and the bulb should be off.

The source for the #2 wire will work either jumped from the alternator battery terminal or wired back further into the harness. GM did it both ways.

I have run a "really" large pulley on an alternator, it still worked; but did discharge at idle with the lights on.

I guess I would double check that it is wired the way the you think, that the indicator light socket is the right style, and check that all the connections, including grounds are good. Must be something off a bit, since it should work.

 

What makes me think it is the pulley size is that when the motor is running and I put my voltage meter across the battery posts, I am getting less than 13 volts. Seems that the alternator is not charging enough at that low rpm. Gotten the same result from two different alternators.

 

Here is an old thread that covers some of these same questions:

http://www.jalopyjournal.com/forum/threads/gm-10si-3-wire-alternator-question.217154/

 

Connect T2 to the battery side of the starter solenoid.

 

Thought you had said earlier that it didn't work, even when you revved the motor.

 

Had this experience now with two different alternators:

When the motor is running (10si alternator with oversized pulley)...voltage across the battery posts is 12.4 volts. Should be 13.4 or so if the alternator is charging correctly.

With the motor running and headlamps on and blower motor for the heater on (to create more load), voltage across the two battery posts is a little over 13 volts. Much lower than it should be if the alternator were properly charging.

With the motor running at idle or revved, the warning light stays on.

And if I measure the voltage off terminal 1 with the motor running (ie, jumping from terminal 1 to a good ground), I am NOT getting 12 volts off terminal 1.

That said, the only way that I have wired #2 terminal is to make a short jump wire over to the B+ post there on the alternator. I should do like several articles have suggested and run the wire from #2 back to the solenoid switch, and the alternator ground back to the battery and see if that makes a difference...along with changing to the smaller pulley.

 

the GM alternators turn off to protect the battery ( because they draw current ) below apx 550 engine rpms ( apx 1200 shaft rpm on alt ( apx 2.5 the speed of the engine ) , one of the reasons why you have to blip the throttle on one wires to turn it on ), and yes the larger dia pulley will slow it down considerably ( you have to take in account all the pulley diameters to get the belt foot speed thats needed ) try the smaller diameter pulley , also how small is the crank pulley as if its small in diameter it too can cause a low belt speed , you might have to change both thats why on some cars they have a 2 step pulley on the the crank or water pump one for the higher rpm to drive the alt and a slower one for power steering or a/c , you can get a hand held tach and measure your alternator shaft speed at idle , then see if its near the turn on/ run speed .

 

If there is not a typo in your comments ^here^, it appears that your alternator is charging, and there is an issue with the warning light circuit. To me, "a little over 13 volts" would indicate that the alternator is carrying the load of the blower motor and headlights, PLUS slightly charging the battery.

 

What voltage do you have on the wire at the light that you connected to the fuel gauge? Usually the instruments operate @ 5 volts via a voltage reducer. If you have after market gauges they may be 12 volt.

If you do have 5 volt you need to connect the light to a switched 12 volt source. You may not be putting enough voltage on the alternator to excite it.

 

actually you need .6v over the 12.6v of the battery to say its charging properly ( 13.2v) otherwise its drawing from the battery and the alternator and might actually be discharging the battery . proper alt volt levels are 13.2-14.4 volts ( in a sever discharge like a jump start they sometimes go to 14.8 -15.2 V for a few minutes to get a charge going )

one thing I forgot to add , make sure your battery has a 12.0 charge in it , if its lower than 11.8 volts the alt may not turn on as you need juice to create juice , not like a generator which has a constant magnetic field not a electric generated field .

we had a 81 pick up that would start and run but the alternator wouldn't charge unless you flashed it with a 12 v source . replaced the alternator 3 times before we changed out the battery ( had 2 cells going bad and was making 11 v ) and solved the problem.. we figured it out when it would work only after you charged the battery and then started the truck and the alternator kicked right in .

 

Pulley size on the alternator is way too big, but the Offy 2" pulley should be here tomorrow. That will change quite a bit, as the crankshaft pulley is then 3x the alternator pulley.

I read the specs on the alternator (included in the box it came in) and the unit doesn't even turn on until 1800 rpm (600 on the crankshaft). But the alternator at that speed is still a net user of current. It doesn't become a net producer of current until a much higher rpm, which explains why merely blipping the motor didn't make the warning light go out.

Oh, and how about those warning lights? Cheap plastic with wheat bulbs. I have a set of SW vintage lights on the way with metal casings and conventional incandescent bulbs that require more draw.

I will rewire the warning lights' power source to the cold side of the ignition switch so that I know I am getting 12 volts with the engine keyed and motor turned on.

I additionally neglected to hook up a long enough sensing wire to terminal 2. A run longer than a pigtail is required so that this sensing wire has enough resistance to inform the alternator to produce more current.

The question: what circuit should I connect the sensing wire end, opposite to terminal 2? Some people say the the horn circuit. Others have said the cold side of the ignition circuit at the key. Others have said at the positive side of the starter solenoid.

The wire is hot all the time, so naturally my concern is having a long run of unfused wire.

Add a fusible link? Add a fuse? Put it on the horn circuit since that run is already fused?

What are your suggestions, and thank you again for all your help here.

 

Fusable link at the alternator is easy as falling off a log and smart.
Close to the main distribution of power, however yours is set up.

 

That is an easy and accessible place to put it.

 

Too check if the alt is putting out run a hot 12v to the field post when the car is running. This will make the alt put out max volts. Then you will know if it is charging.

 

proper placement of the sensing wire is ussually at the battery or a heavy cable leading to the battery ( post on gm style starters or the hot side of the ford solenoid ) , we try to do the battery as it acts like a filter and takes out the spikes and will see if the system is drawing down better than if you ran it inside the car were it can be covered up by being infront of the drawing device ( which can /will recieve current from both sides if the alt is not making enough ) its a hot lead but not a real load carrying circuit ( like the blower motor or headlights ) so getting hot should not be a worry just keep it from hazards . you should not fuse the sensing wire as if the circuit is interupted the alternator will go full on and can melt the harness down in seconds . there has been cases of the alt going into what we call supercharge and making 60-100 volts and maximum amperage .

 

Here is an article that specifically warns not to put the sensing wire at the battery. It recommends placing it after the fuse block so that any accessories or parasitic loads might be sensed. It is in the "Warning" section of the article:

http://www.junkyardgenius.com/charging/delco01.html

 

Try wiring it like GM did, I use the 10si on all my cars (even non GM). They came out in '73 and GM ran the power wire to the horn relay (my converted from a generator GM cars are like this). You won't see 12v on the #1 wire with it running (it's dimmer with a test light) and you loop the #2 wire to the BAT+ on the back (which you have). Make sure the case has a ground wire to a GOOD ground (frame or battery). The warning light will come on with the ignition in the "on" position as a bulb check then go off when running, assuming the alt is good. The regulator grounds inside if there's a problem which completes the circuit and turns on the light, the bulb acts like a resistor to send a little power to the alt to start the charging process. If the light stays on then either you have a bad alt (I've had more then one bad electrical products that was new in the box in a row) or a problem with the circuit. Take the wire off the alt and see if the light goes out, if not repair the circuit if it does get the alt checked (could have a leaky regulator or diode pack).

 

Yes, that is precisely the wiring layout I now have.

But is a better explanation for what is going on here...the alternator simply isn't spinning fast enough. The only way I know that is through the warning light. It is telling me that at idle the battery is in discharge, and that it won't start charging until I am up to speed. If the alternator were a one-wire, and I were reading the gauge, the volt gauge is reading 12 volts, but it is reading battery discharge. The alternator isn't spinning fast enough to produce current, but the volt meter can't tell me that.

An amp gauge would, but most guys don't run an amp gauge.

For my flathead, I now have both the Speedway pulley and the Offy pulley for the alternator. Measured from the outside, the Speedway is approx. 4.5' in diameter; the Offy is 3.75" and the stock Chevy is 2". Huge, huge difference in how fast the alternator spins. The pulley size is simply too big, and the alternator isn't producing enough current at low speeds.

If a battery tender is used all the time on the vehicle, the loads are kept minimal, and the battery is never allowed to run down, this inadequate setup probably doesn't make much difference in my case. Other than the warning light will come on at idle.

I'm off this morning to an alternator shop to have the regulator replaced with one that kicks in at a lower rpm. These modifications are commonly found where guys are using these 10si and 12si units in tractors. I'll post up what he's able to configure for me.