Something I did not notice before or something keeps changing? Tested volts again with everthing on the volts went way past 16 volts when I gave it some gas.Changed wire ,ran from the # 2 pin on the alt to the thru firewall hook up and volts still past16 volts giving it some rpms.Turned everything back on except the head lights it went to 15.8 volts.Turn headlights back on it goes past 16 volts.Turn everthing off it reads 15.2
Last week it read 15.2 with everthing on.Whats
going on??

John,Peter what do you think?

That's strange. Did you meaure that voltage at the connection for the #2 wire?

It sounds to me that either the alternator isn't regulating the voltage or there is a bad ground.

You need to have a decent sized wire connecting to the battery, body, engine and frame all together. You need a main power wire from the battery to frame and frame to engine to provide the return for the starter. Then, run something like a #8 from the engine, battery or frame to the body. Remeber, the grounds need to be sized as heavy as the positive wires.

Peter

This car is grounded to death.It has a large cable
the same size of the main cable running to the firewall thru connection.One running to the cage,one running to the frame,one large running from the block to the frame and one running from the block to the firewall.Maybe I need to pull the alt and have it rechecked?Crazy thing!Thanks,Driver

Ever hook up that lead to terminal #1? It has a purpose.

Yes, I did. But it doesn't make any difference concerning the reading of the volts. At least it doesn't change when I hook it up or disconnect it. The only thing I noticed when it is hooked up is the generator light comes on.
Thanks, driver

Originally posted by driver:
Yes, I did. But it doesn't make any difference concerning the reading of the volts. At least it doesn't change when I hook it up or disconnect it. The only thing I noticed when it is hooked up is the generator light comes on.
Thanks, driver Interesting. When the alternator is running the GEN light should go off. If it's not going off with the engine running try:
Engine off, unplug the connector. Turn the key on and measure the lead that goes to #1. That wire should have 12 volts. (That 12 volts comes from the ignition switch).

This car is driving me crazy.Took off alt and went to the shop that built it.Put it under a heavy load tested fine,14.2 under a load.Put it on a 40% load for 30 mins and it tested fine(14.2)
Tested amps 90.Took it back home hooked it back up
and ran the jumper off B+ alt - #2 plug in plus ran the brown wire to the #1 plug in.Alt 14.2
firewall cable 13.6 plug in #1 13.8.Turned everthing on fuse box 12 alt 13.2 firewall cable 12 the fuse box was really a little less than 12.
Volt gauge inside of car was reading below 12.I don't get it.The man that built the alt said what John had said about the #1 plug-in.I just don't know where to go with this thing next??Thanks

Belive Peter suggested moving the #2 wire off the B+ terminal and tying it someplace else. Think he suggested the horn relay. Tried that or am I simply forgetting stuff again?

I should have asked where you were reading the high voltage? When you tied the #2 wire to the horn relay the stock fuse panel and wiring should not have read over 14.2V. But, the alternator wire and the battery could have been higher.

In all cases, the firewall connector and battery should read at pretty much the same voltage. At these current levels you won't get hardly any voltage drop across that #1 guage wire.

Does the wire to the firewall connector also run the starter or is there a seperate starter wire?

I think your best bet is to connect the #2 alternator wire to the firewall connector. Try that and tell us what you get voltage wise. The firewall connector is the main power connection point for the car so that is the place where you want to regulate the voltage.

When I look at the voltages you just posted you're getting 13.2V at the alternator and 12V at the firewall connector. So, the wiring from the alternator to the trunk mounted battery and back drops 1.2V. Connecting the alternator #2 wire to the firewall connector will compensate for this by increasing the output voltage.

What rpm is required for the alternator to produce full output current? You should be able to get that from the rebuilder. What pulley ratio are you running from crank to alternator? The wiring method will only make the alternator produce what it's capable of.

Peter

So far, I agree with Peter but maybe I am not seeing something else.
*A question about the wires on your horn relay.*
Do you still have the original large power wire that went to the bulkhead connector tied there? This wire originally supplied the original fuse block in the car. Thinking along with Peter's suggestion about moving the sense line to the firewall connector, the original fuse block line may also need to be moved there. (Keep thinking that the problem may be related to having 2 large loads separated from each other)
If I'm seeing things right this is an unusual set-up. Not that it can't be made to work.

I'll recheck everything again in the morning and let you know.When I was getting 16+ volts at the alt I tried it both ways on the # 2 pin.Off horn relay and off the firewall but nothing changed.I'll get more detailed with results next time.I checked so much I can't remember everthing.
Driver

If you measured 16V at the same place the #2 wire from the alternator was connected you MUST either have an alternator problem or a bad wiring problem (ground or power wiring). I just can't think of any other reason this won't work.

The #2 wire is the sensing wire for the alternator. That is the terminal that the internal regulator measures to adjust it's output. So, the voltage where the wire is connected should not go above the 14.2V that the regulator operates at. With a heavy load, you can draw the voltage down but it should never go above 14.2V at the point where that wire is connected.

What size of wire were you using when you connected the #2 wire to the other locations. The stock wiring harnesses I see have what looks like a 10 or 12 gauge wire connecting that terminal up. It must be heavy for a reason since the factory wouldn't waste the heavy wire for no reason.

Another thing to try is to move the meter -ve lead around when you're measuring the voltage. For example, when measuring at the same spot try putting the -ve wire on the body, frame, engine, alternator case, etc. The voltage should always measure the same or the ground is bad. Similarily, you can put the meter leads at each end of a wire to measure the voltage drop across it. Remember, every wire will have some voltage drop but with the wire sizes you have the voltage drops should be very small, likely in the 0.1 to 0.2 volt drop range as a maximum.

I think you need to eliminate a possible bad wiring connection. Crank it up with all the loads and look for a hot spot in the wiring because that'll indicate a poor connection.

If you are sure about the wiring then ask the alternator rebuilder about the #2 terminal being used as the sense wire and connecting it to another spot besides the bat post on the alternator. Maybe he did something funny in the rebuilding (what I wouldn't know). Maybe you need to take the car to him and confirm the wiring method you're using with him.

I can tell you one thing. If you want to run it with the #2 terminal connected to the Bat post on the alternator you will likely have to increase the wire size of the alternator to battery run and still live with a low voltage in the engine compartment. As an example, 8awg is 0.67 ohms of resistance per 1000 feet. So, 0.67 divided by 1000 is 0.00067 ohms per foot. 25 feet would be 0.01675 ohms. Times that by 90A and you get a 1.5V drop. Scary, huh? So, if you have 14.2V at the Bat post on the alternator the best you can get is 12.7V at the battery. You then get less after the wiring run back to the front of the car. By moving the sensing wire, the alternator will produce 15.7V at the Bat terminal so that you get 14.2 at the battery.

So you know, 1awg is 0.126 ohms per 1000 feet and 25 feet would have a 0.28V drop at 90A. So connecting the #2 terminal to the firewall end of the #1 wire should not result is a voltage at the battery much over about 14.5V.

Peter

One thing the alt builder said about the #1pin didn't make any sense to me.I noticed when he was testing it that he had a wire running to the #1 pin which I ask him what was the reason for it.He
said to energize the alt off of a key switch.The way I took it was with-out a hot wire going to the #1pin the alt wasn't charging? I thought thats was what the jumper wire running off the b+ alt to the #2 pin was for? This alt went way past the 16 volts range but it didn't do that the 1st time I did the test.I had thought about getting a alt from a buddy to see if it makes a difference.
I'll get busy today and try many different ways and this time write it down.Thanks for all your help on this on going problem.Driver

Pin 1 is the field and requires an excitation voltage to the alternator. If an alternator is new or has sat for a period of time it won't start without the excitation voltage from the key switch. The idiot light was added in there as a "extra feature" and is not the reason for the wire.
Pin 2 is the remote sense line. It's the line that controls what the alternator puts out. If everything is close together, tying it to the back of the alternator works. If things are spread out, moving it away from the alternator and closer to the heavy loads works better. The sense line then measures that remote point and raises the voltage slightly out of the alternator.
Unless I misread things you have 2 points that draw a heavy load while normally there is only 1 point. The 2 points are
1, The original fuse block
2, The new firewall connector.
Moving the remote sense wire, from Pin 2, to the firewall connector should help. As the big power items come on, the remote sense wire will see the voltage drop on the firewall connector. The alternator B+ voltage will then go up to compensate for the heavy load. In other words, we don't care about the voltage on alternator B+. We only care about the voltage on the firewall connector.
That should take care of the problem with the firewall connector. Since you have a very large wire from the firewall connector to the battery, the voltage should almost be identical. This should keep the battery charged.
The next problem that may occur is the voltage to the old fuse block. I believe you still have this tied to the horn relay. After you have the system controlling the firewall connector, this point needs to be measured. If this point is too low, the wire to the fuse block, in the harness, should be moved to the firewall connector. However, one thing at a time.

TEST #ONE,not running-jumper wire on the b+ to #2
wire on b+ to firewall.Not running=battery12.2
alt 12.2 horn relat 12.2 #one pin brown wire8 volts fuse box 12.2
TEST#2 running rpms 2,000-3,000 eveything on
fuse box13.2 horn relay13.2 #one pin brown wire14.2 alt 14.2 firewall 13.4 battery 13.4.Going to do some more testing.Be back.

Hopefully you are taking the #2 wire off the alternator B+ and moving it to the firewall connector. Move only the #2 wire. Leave the other wire on B+.

The results I posted the 1st time I added a wire to the b+ to the firewall leaving the jumper wire going from the b+ to the #2 pin hooked up.This time I removed the jumper wire from B+ going to the #2 pin and put the wire on #2pin to the fire wall leaving the wire from the battery hooked up to to the b+.In other word I just unpluged the #2 pin and ran a wire from the #2 pin to the fire wall.This time volts way out of line.Alt 16+,firewall.12.6 give it 3000 rpms goes up to 14 volts.#1 pin 16+ with 3000 rpms,fuse box 11.8 give it some rpms 3000 14 volts.The more you push the gas the higher the volts go hooked up this way.The other way the kill switch works about half right,kills motor but fuel pumps and ele fans keep running because the extra fuse box is tied into the main battery cable running from the trunk.When I run the wire from the b+ alt to the fire wall it's feeding the fuse box juice at all times because of the wire running off the battery to the b+ alt.Im getting to the point of gutting the whole wire system and buying a painless set up.The 1st posted results looked pretty good don't you think?If the results look ok I guess I'll need to find another place to run the fuel pumps and so on?Does the 1st results look ok?

My thoughts;

First off, the wire from the alternator to the battery is WAY TOO small. Run another #8 in parallel or switch to a #4 wire as the MINIMUM. A #2 would be even better. You need to change this first. In your latest tests, see how the alternator voltage goes up to 16+V while the firewall connector is at 14V? This CLEARLY indicates that the wire from the alternator to the battery is too small.

Secondly, The alternator is too small for the load you're putting on it. It's not capable of producing enough output at idle when fully loaded. Once you upgrade the charging wire, you will have a better idea of how well the alternator will work. I believe a 140A unit would probably work OK for you. You're looking for a larger higher output unit here that was built specifically for the high output current, not a "beefed up" rebuild small unit that was origionally built for a lower output current.

Thirdly, if you want the disconnect and battery to stay where they are and still be functional, the car really must be wired as I've recommended. So, you either need to move the battery and disconnect to the engine compartment or follow the recommendations as posted in the first 2 comments above. It kinda sucks, but that's the way it is.

Lastly, in your latest tests, see how the voltage goes up to 14V at the firewall and fuse box when you rev it? This is EXACLY how it should work and it will work MUCH better at the lower rpms once you follow the above recommendations.


Other observations;

Are you disconnecting the main wire running to the firewall conector with the kill switch? If not, where exactly is it wired?

In your post starting TEST #ONE, the voltage at the firewall, battery and fuse box only went up to 13.2V. This isn't working as well as in your last post with only the #2 terminal wired to the firewall connector where the voltage went to 14V.

Do not worry about any of the voltages you measure at the alternator. The voltages at the Bat and #1 terminals on the alternator DO NOT matter. Only worry about the battery, firewall, and fuseblock voltages.

The Painless wiring will not help one bit.

Finally;
This is what I want to see voltage wise if you do further tests;

Battery @ idle =
Firewall @ idle =
Fuse Block @ idle =
Alternator Bat @ idle =

Battery @ 2000rpm =
Firewall @ 200rpm =
Fuse Block @ 2000rpm =
Alternator Bat @ 2000rpm =
Write them down this way too because it's much easier to read then all mushed together in one sentence.

In summary, you have to decide if you want to add heavier wiring for the alternator or move the battery back to the engine compartment. Then, after you see how much that helps, you may still need to upgrade the alternator.

Peter

One other comment. In an ideal world, the voltage should run about 14.2 volts. Thats the ideal voltage for the battery and accessories.

Peter

Thanks PETER,I'll get some heavy wire today at the parts store and see what I can get done.Im working on the car and in the middle of switching jobs at the same time.So you think I would be better off going to jegs and getting a 140 amp instead of getting this one beefed up?High $$$
but if that takes care of the problem thats what I will do.NOT UNTILL I CHANGE THE WIRE.Price at jegs for a 140 amp is $250.00 but I'll see where the wire change puts me 1st.I take that back I found another alt in the jegs book 140amp for $177.00 but it's made by tuff stuff which sounds cheap?

Bought a #4 cable and ran it from the battery to the b+ alt with the jumper wire to pin#2 off alt b+
Idle
alt b+ 14.2
battery 14.2
fusebox 14.2
firewall 13.8
I went right back and checked it again at idle.
alt 14.2
battery 13.4
fusebox 13.6
firewall 14.2
Again at 2,000 rpms
alt 14.2
firewall 13.8 and then it went to 14.2
fusebox 13.6
battery 13.4
While in the car rpms at 2,000.On the alt b+ I
noticed something strange while watching the analyzer.IT SPIKED.Jumped from 14.2 and then right back up.Happens real fast but not a steady thing.Did it about four times.Thats where I think my miss is coming from.It did it on the alt b+ and the firewall.This car has a noticeable miss and I think it's in this electical system.I have been trying to find this problem for over two years.I went thru the wires and msd three times.Had msd walk me thru it twice and it's all installed right.Changed everthing twice in this car and I mean everthing.I just ran this cable down the side of car the wanting to make sure it changed something before going thru the trouble of running it inside the frame rails.I even took it to a shop and wasted about $400 because they could'nt figure it out.Tried to tell me it was a fuel problem but I did'nt buy that and still don't.This was about a year or so ago.I know the volts should not spike like this.

Tested wire straight from #2 pin to firewall and #4 cable still hooked up.
Idle
battery 14.8
fusebox 14.8
alt b+ 15
firewall 15
tested at 2,000 rpms
battery 14.8
fusebox 14.8
alt b+15
firewall 15
Tested everthing on
Idle firewall 12.6
alt b+13
fusebox 12
battery 12.4
Tested everthing on at 2000 rpms
firewall up to 14.2 but slow getting there
alt b+ 14.2 but slow getting there
fusebox 12.4 but slow getting there
battery 13 but again slow getting there.

Which way did it spike? Up or down? How much? It can't be a short because it would have burned up by now.

Have you always been running that same alternator? I remember that you've changed all of the ignition stuff and even the engine but what about the alternator? See below for why I suspect the alternator.

The fuse block measurements are from the factory one, right?

That #4 wire seemed to really help. I'd install it permanently. With it, you could probably run the car OK with the #2 terminal just connected to the Bat post. The voltages will be a little low but it would work.

You are using a good heavy wire for the connection to the #2 terminal, right? Something like 12awg.

The numbers really help. You didn't specify in the second last post what the load was but I have to believe it was unloaded. The numbers you posted second last are somewhat strange. I'd expect 14.2V everywhere all the time. Without any loads it shouldn't fluctuate at all, even at idle. The voltage shouldn't be going between 13.4 and 14.2 volts. You didn't specify what loads you added so if you did have some loads post it again.

The last post looks really good except that the alternator isn't regulating correctly. It should hold the #2 terminal at no more than 14.2V. Since you have the #2 terminal connected at the firewall connector, then the firewall connector should also not go over 14.2V. You need to call or even visit the alternator rebuilder with the car and get his opinion on this. Maybe it is a 14.8V regulator in it so call him and ask this?

The voltage drop at idle in your last post isn't a big deal if you're not going to be idling with everything on much. Being a drag car though, I bet you do idle with that stuff on.

Try this, disconnect the #2 terminal completely and start the car. Does the alternator produce output voltage(voltages rises to 14V when started)? If it does, there's a 1-wire regulator in the alternator and moving the #2 wire won't work right. I can't see this but test it anyways.

The voltages at the fuse block are always lower than the firewall connector. This is indicating that the wiring from the firewall connector to the fuse block is also not heavy enough. But, save this until you get the charging system producing the voltages you want. One problem at a time.

See how the fully loaded voltages don't stay up at idle in the last post. This is an indication that the alternator isn't producing enough power at idle.I think you must be running close to 90A with full load which is a lot for any alternator at idle.

The builder should be able to tell you what rpm is required to get 90A. Maybe you already know from the last visit. Check the alternator rpms at idle by the formula alternator rpms = crankshaft rpms X crank pulley diameter divided by alternator pulley diameter. What i'm saying is that your alternator may work with a different pulley ratio that increases it's rpm's at idle.

To properly select a new alternator, you need to find out the current draw with all the accessories running. Then you can select the alternator. What you then need is the performance curve for alternator. This is a curve that shows output current vs rpm for the alternator. You need to select the alternator rpm required for your load current. Then, select the correct pulley ratio to get this alternator rpm at idle. The curve will show alternator rpm's not the crank rpms. If the alternator rpms and pulley ratio is unrealistic then go to a more powerful alternator until you find one that is acceptable.

**********

Other alternator info;

Taken from a search here "The mid 90's Olds Silohettes with the 3.8 and rear air have a 140 amp alt"

Here are some other Summit examples for reference;
SUM-G1669 - Is a GM 12SI type with factory max output of 94A. $260
PWM-47861 - Is a GM CS-130 type that could be had from factory with 140A output. $140
PWM-48203 - Big 200A unit that will perform but costs $350.

The above is to show you what the alternators are, not a recommendation.

Peter

I forgot. Most alternators need to be running at a minimum of 2400rpms to begin producing decent power. This means the crank pulley needs to be about 3 times as large as the alternator pulley to get decent output at idle of 800rpm. The problem is that you need to keep the upper alternator rpms below 18000 or 20000 rpms so in the above3 example 6000 engine rpms would be 18000 alternator rpms.

Peter

I spoke to the alt builder the other day asking him about building a 140 amp alt which he said he could but it would have to be a one wire deal and the only problem with a alt like this is it has to have some rpms before it will kick in at all but if Im right all alts are pretty much that way.
I just wish I had a H.E.I dist to do some testing with because I still have this feeling that it will stop the miss.Don't won't to go out and buy one just for a test.When I 1st fired this new motor up I had a friends H E I and I don't recall a miss like this but when I put the msd in it seemed to be there.I don't know if a H.E.I will support a low 10 second car on nitrous?The spike I spoke of goes down from 14.2 to around 13 volts but it happens so fast it's really hard to get the true reading.The problem I have with this car was there when I 1st bought it which me and a few friends thought right off the get go it was in the wires or a volt problem so I changed the dist,plugs,plug wires,cap and coil which did not cure the problem.Next I called msd and went thru all that which was all correct.I cleaned everthing up because it was a mess.Next I replaced everthing in the car like msd box and all the other parts related to it,alt,battery ,wires ,cables,starter and the list goes on.A freind of mine said a friend of his had a problem like this that the car would not run right with a msd set-up once they put the HEI back in the car it ran good but didn't have a answer for why it acted like this.Said they could not figure it out.

Ran the #4 wire along the frame and retested everything which I think will be ok.I tested the msd ignition red wire while the car was running which was 14.2 and then put it under a load with everthing on which it went down to 13 but gave it 2000 rpms it went back up to 14.This should be more than enough for the ignition.Everthing eles at idle tested 14.2.Still have this miss and I'm
starting to think that the guy who thought it was a fuel problem may be on to something.I took the fuel cell out and took out the foam blocks thinking it could be blocking of coming apart causing a problem.Cleaned it out and put back in with-out the foam.Tried it out but no change but got to thinking about the fuel return line which I could see real well with the foam out.Seems to me there is a lot of fuel returning to the cell.I mean a lot which leaves me to wonder how much is getting to the carb?Seems to me there is as much returning as there is going.Anyway, Peter I really appreciate all your help and time.I also learned a lot going thru this.Thanks again and have a great weekend.Driver

Yup, all alternators need 2000 to 2500 rpms before they begin generating any amount of serious power. Read the stuff I posted before. Pick pulley ratios to get the alternator at around 18000rpm at your rev limit.

Idle with low voltage is OK as long as it comes up with some rpms. You just can't run at idle much or the battery eventually goes dead.

Did you just leave it with the #2 wire and Bat wire connected. I think the builder has done something that doesn't allow the #2 wire to work as the sense wire correctly. I'g going to test it on my car because I have a stock type 10SI with the #2 and Bat jumpered on a mostly stock car. It works like this so that's how I set it up.

I think you still need to address the firewall connector to fuse block wiring. There is too much voltage drop there for my liking. 1V is a lot of drop for a 12V system.

A sudden voltage drop without any accessory turning on is either the alternator or an accessory problem. You can't have a shorting wire causing this because it would have stuck shorted to ground and either blown a fuse or burned. An accessory could be spiking on causing this. For example, something funny in the electric fan relay could be causing the contacts to chatter on which could happen so quickly the fan doesn't move and yet it bumps the motor load onto the sytem for a split second. Unfortunately, this is really hard to trace.

The only other idea I'd have electrical wise is that the pick-up coil feeding the signal to the MSD is picking up noise so it either adds extra ignition pulses or misses them. Those wires should be short and twisted together. You can also run a shielded wire for them to see if that helps. If you have solid ignition wires they will be causing the problem. Also, don't coil-up the excess wire because the coil amplifies the noise pick-up. Remove any excess wiring so the harness is as short as possible.

Lots of return fuel flow doesn't necessarily mean that the carb isn't getting any fuel. You need a pressure guage at the carb to know that it's always got pressure at it's inlet.

Peter

I left it with the jumper wire on the B+ TO #2 PIN
I got 7psi at the gauge but Im going to by-pass the return line to see what happens.Tried this before and could not get the fuel psi below 15.Running a return line is good but I would'nt think it's a must.I just can't figure out why I can't get it to adjusted with-out hooking back up the return line? There is a lot of cars out there that don't run a return line.Driver

You need a dead-head or 2-port type regulator to run without a return.

If there is always pressure at the guage then I don't see how you're not getting enough fuel.

Peter