Im trying to trouble shoot a charging problem, I cant seem to get an alternator to put out enouh\gh amperage, Im on the 3rd one now, so Im pretty sure its not an alt, and everything else (batt, cables etc) has been replaced/.
So my question is, when the car is running, should both wires going into the plug read the same voltage? the batt wire is reading the same as the batt within less than a 1/10 volt but the other wire is almost 2 volts less, would this cause it to not charge?

thanks for any help

 

First of all Monte, what do you mean by enough amperage? Is it at least charging? There are two factors one must consider when trying to troubleshoot a charging system. One is current, and the other is voltage output. Both are related but for simplicity let's just look at voltage because it is the easiest way to find out what is going on. Does your guage show charging when you rev the engine? If so the alternator is working. If you have a light then get an inexpensive voltmeter and check the resting voltage(engine off) and then start and give it a little gas to bring it off idle. Did the voltage go up. Take these readings right across the battery terminals. If it went up then the alt is working. Current or amperes can only be measured properly by the use of an ammeter inserted between the heavy red wire from the back of the alt to the battery. The meter must be capable of reading the max output the alt is capable of. Also a load of some kind, usually a carbon pile is needed to force the alt to charge and handle the output. Strictly speaking usually if the alt. has voltage rise when running it is OK all around. Do you know what series alt it is? From about late 86 on up OE units were the Delco CS series. These units only need two wires to work. The heavy red wire on the back goes to the batt through a fusible link(most models), that is the feed to the battery for charging. The two wire plug on top should have one heavier red wire. That will show 12 volts when key is turned on. The other wire can be used for a charge light or guage and usually will have a resistor in the circuit(accounts for the slightly lower reading). These units get thier ground through the case, are all engine grounds OK? Many people think they have a problem when at idle with accessories on and the guage drops down. Perfectly normal. Also did you upgrade to a heavier alternator? Remember the more amps the alt is rated at the LESS you will see when idleing. If you still have a problem try to give more info if you can>

 

right now I have an amp guage installed as you described earlier, it reads 15 amps weather or not the lights are on, heater, stereo etc. with nothing on, the batt voltage will climb very slowly, like 1/100 volt every 10 seconds with the lights on you watch the batt voltage drop about 1/10 volt every 10 seconds I havent run it long enough to get less than 11 volts before I shut it off and put the batt charger on it to get it back to 12+ volts.
According to my GM service manual with the key on engine off both the wires to the plug are supposed to read batt voltage, which they do, but I checked them while it was running to see if it stayed the same, well the main batt wire does, and the other wire drops almost 2 volts and I was wondering if that would cause it to not be putting enough amperage out that is what actually charges the batt anyway. I checked the body grounds cause the only thing I have done to the car since it used to work was install a set of SLP runners, so I figured maybe I didnt get a good body ground, or get it back on ok, well if I do an OHM's check from the neg post on the batt to the body, anywhere just scratching through the paint, it ohms out to 0 ohms. Im now in the process of tracing the wires to see where Im loosing the voltage, but hope that someone has a good idea that can get me on the right track
thanks

 

I pulled manual for my 89 camaro. They show the thinner of the two wires at the plug going back to a fuse in the fuse block. If yours is wired the same and they should be then the 2 volt drop may be a clue. According to Chilton the fuse is labeled FAN at the fuse block. Earlier models show this fuse as being marked CH/FUSE. Any bells yet? Some time ago I printed up the online service manual for the CS series alternators, and it comes in handy. You can get it for free from www.alternatorparts.com. Let me know how you make out. Did some more checking, the wire that is 2 volts low is most probably the sense line. It makes sense to me that they would most likely tie into the line for the electric fans on my model since they draw a lot of current on startup. I think if you find out why that wire is low you will fixx the problem.

 

ok well I checked voltage at the fuse you were talking about and it reads whatever the batt voltage is, so I start back probing and on the outside of the car its about a volt or so less, now Im in the process of trying to figure out where its going, but with the fuse out and the alt plug disc my ohm meter shows shorting to ground I disconnected the body plug and going from the wire off the alt plug to ground it still shows 0 ohms and then testing to see which pin it connects to on the body plug, I get continuity to aprox half the pins on there, reading the schematics I cant really tell if this is correct or not but Im trying to see if there is something wrong in that area. (all these are tests are coming off the brown/white stripe wire)

one thing I did find from playing around, if I taped into the brown/white wire at the alt when it was running and then touched it to the batt wire I could watch the amp guage jump up to aprox 60 amps, the way I have it hooked up while doing this is, all the accessory wires that were orriginally on the starter are now connected at the alt, then the wire from the alt to the amp guage then into the batt, (this is to see if it puts out more amps than what is being drawn) when I leave it alone it sits right at 0 amps with very little fluctuation (not sure if its just the guage being bounced or actuall amperage) then when I turn on the lights it shows a draw.

 

It looks like you found the problem. I am always reluctant to suggest someone putting a voltage to a point unless I am sure they are somewhat familiar with working on auto electronics which you seem to be. By putting 12 volts to the sense line you have effectively solved your problem. Now it is just a matter of finding the wiring glitch. Don't overlook the harness getting near the exhaust manifold or possibly water corrosion. In all reality you could tap into just about any 12 volt line to activate the sense. I would try to dog it out, because you may have more than one problem brewing. One thing confuses me, if you are getting 0 ohms to chassis gnd then if you put 12V to it something should have smoked. The reason you are reading between wires is beacuse they are all probably tied to 12 volts through the fuse panel. Find out which fuse feeds that wire, as it may vary from model to model and pull it from the panel. That should provide some isolation for testing.

 

well last night I tore the wiring harness apart trying to find anywhere that may be melted together from the exhaust or anything like that like you mentioned, now that I have pulled the sense wire almost all the way out of the wiring harness I did anoher Ohms test to the body plug, and Im not getting any readings on it now, so Im not sure if I accidentally fixed or screwed something up, I havent gotten everything hooked back up yet to check and see if I did either way or not but hopefully Ill have time to get that done today.

 

ok Ive rewired the alt to where the sense wire is connected strictly to a batt wire instead of a key on hot wire should work just the same well I took the car yesterday to the local Checker to have them test it with their little OTC scanner and Im still getting the same prob, not enough charging volts, when I hooked it up like this before and put an AMP guage in between the alt and the batt it would surge with the engine rpms up to 60 amps with or without lights on which was more than it had done before, which was nothing. Im confused as hell now.

So today Im going through the wiring again and I still get a 4.2 amp draw and Ive pinpointed it to the VATS module, this seems way high for something like that to be pulling but I may be wrong, and I dont see from any of the schematics where this would cause a charging problem. Cant eliminate it without getting a chip burned.

Im ready to toss this alt out and try one of those 1 wire jobs from www.alternatorparts.com but Im leery of buying one and not having it work either.

Youve gave good pointers so far any ideas??:hail:

thanks
Jack

 

Jack, stupid as it sounds I never looked to see where that sense wire went. I pulled some wiring diagrams for different cars and they all seem to feed a sense to the blower motor or the electric fan circuit. Makes sense now that I think about it. Even if all wiring is clean and intact there is always a voltage drop on a circuit with a heavy load. It looks like they want to bring the voltage up for the line that is lowest to maintain a constant 12 volts. When you say volts are low now what do you mean? If you battery is charged you may not see much of a charge, especially if you have now tied the sense line directly to the battery. Remember, if that sense is up near battery normal voltage the alt will not charge very much. Actually, you may be OK now. Leave the headlights on for an hour or so, then check charging voltage. You may find that all is OK. These alternators will SMACK the battery with a lot of current until the battery comes up to terminal voltage and that usually happens in the first several minutes. To check current output check it with all accessories running, honestly you have covered all bases. Keep me posted. The 4 amp draw I don't know. What happens to the draw if you disconnect the alt? Maybe with all this work it got damaged. The VATS module is a relatively low current device, probably on the order of milliamps. If it shorted however, it is possible. Disconnect the alt wires, even the heavy one to the batt and put the ammeter in series with the battery lead. Then start pulling fuses. 4 amps without engine running is way too much.

 

true, never even thought about that, but thing is, my fans have been rewired since the day I installed the motor, they are aftermarket fans with their own control's and relays, one kicks on when the key is on, and the other just depends on what the temp gets to, I have a GM service manual and other than just tracing the wiring diagrams, I decided to actually read it, and what it is saying makes absolutely no sense at all, this is what it says word for word about the plug in the side of the alt

"Unlike 3-wire generators, this generator uses only 2 connections - batt pos and an "L" terminal to charge the indicator bulb. Use of "P", "F", and "S" terminals is optional. The "P" terminal is connected to the stator and may be connected externally to a tachometer or other device. The F term is connected internally to field positive and is used in service diagnostics. The S terminal may be connected externally to a Voltage source such as battery voltage. " this is from page 6D3-1 of the GM service manual, its the 3rd paragraph in.

this makes no sense, on my set up the L terminal isnt even used since there was never any light and the S is the one that goes directly to the batt, and the F is the sense wire. I wish I had my other computer working cause I would scan this diagram they have of the alternator, because it is showing a resistor for the L terminal in parallel with a light, and the light has a resistor that crosses its terminal so it is also in parallel with the first resistor, maybe thats how they are getting a "less than batt voltage" but it has no diagram for a non indicator lamp system, for just the guage. Reading farther into the book and how they show an off vehicle test, there is a resistor in series from a batt voltage but it still goes to the L terminal.

in the diagram its a block diagram of the alt, batt and indicator light, the P is connected internally, the L goes to the light and 2 resistors in parallel, the F is miss marked as an I and shows no commection, same with the S.

any more good ideas?
Ill try the headlight thing, or a resistor in the wire, I just charged the batt up to get up to 12.5-13 volts, prob dont need to since it hadnt hit even 11.5 yet but figured better get a good start on it
thanks

 

First of all a 12 volt battery consist of 6 cells. Each cell has an output of 2.2 volts when charged. A voltmeter connected between + & - should read 13.2 volts on an almost dead battery which is not much more than a large capacitor. An alternator generates an AC voltage that is rectified to DC by the white module you see through the fins on the rear side. The output varies with the speed of the input shaft. Even at idle you should be reading between 13-14 volts. You can increase idle output current by having about a 10% under size pulley installed on the alternator. If you are using an analog meter, make sure it is at zero to begin. Check the wires on the alternator and battery connection for heat. If either feel warm to the touch you have an increase in resistance which gives a decrease in current. "I=E/R" constant voltage (E) / Increased resistance (R) = less current (I). If all else fails, put on a single wire alternator. ELIMINATES ANY GUESSWORK.

 

You are absolutely correct, I read the very same thing. However they say to consult the vehicles specific wiring. The manual you quote is a reprint fron the alt service manual(both GM). I pulled the serv manual for the alt from that web site I mentioned, that's what had me confused in the beginning. When I traced my wiring I too found it was different. Be that as it may if you tied all 3 to the batt the only thing left is the alt.

 

I did a search on this yesterday and someome had mentioned putting a resistor on the S terminal and running it to an ign hot, I may give that a shot, Ill just have to stop by radio shack and see if they have anything stronger than a 1/2 watt res. I emailed the guys at the alternator web site you mentioned asking about price on the 1 wire regulator and asked about my problem, Im not sure if they will give any technical advice but it dosent hurt. Ill just keep my fingers crossed, anyone want to make an offer on an 87 monte carlo SS with a well running 350 decent black paint job, interior and its a T-Top car?? haha

 

I found that page on the altparts web page, and its just a copy out of the book I have, http://www.alternatorparts.com/cs130_sbpage3.htm figure 3a is the one in my book, and the I terminal is the one that is mis marked for what I have, but none show not using that L terminal, and mine never had it or a light Ill just keep messing around till I toast it, or order one of those 1 wire jobbies

 

I was out working on the car more tonght, retracing wires and even went as far as rewiring the fans to use the relays like the factory had intended even though that was not how I had it set up before to see if that worked, well it didnt. I started out with about a 11.8 V charge on the batt, it very slowly climbed up to 12.1 you could watch the 1/100 of a volt climb every few seconds, so I shut it off and kept hearing something like oil bubbling or whatever, touched the belt and it was hot, and this was only about after 5 min or less of running, touched the pulley of the alt and its hot as hell! thought ok maybe its not turning, puled the tensoiner loose and it is, started the car again its spinning like its supposed to be, its not charging and the pulley/rotor assy is getting hot as can be, any ideas from that? NOTHING externally is grounded could this be an internal short? if so Im just ordering a 1 wire job from alt.com

thanks
Jack

 

Jack at this point everything points to a problem with the alt, maybe something got damaged when working on it. There is nothing else controlling these things, everything is internal. If you have no short on the output line then I would say it's time to try a new one.

 

this shouldn't be so damn complicated. There's the output post and a 2 wire plug right? The output post to the battery. The pink or red wire in the 2 prong plug can be connected right to the output post so it will be getting power all the time. The brown wire needs some kind of resistance between it and a hot in run wire. The light bulb in your dsh does a good job of this. If you have +12 at the pink or red wire and ~+12 at the brown wire and you're still not getting ~14 volts at the outout post at idle then the alternator is pooched or the regulator is pooched.

 

agreed, but the orrig set up didnt have a light and worked great for almost 5 years now, and now this, then the old alt died and went through 3 of them trying to ge tthe damnthing to work and nothing, so I just got one of the one wire alts from www.alternatorparts.com should be here mid of next week and wont have to deal with it anymore