Alternator not Charging Battery
 

Installed a serpentine kit on my 71 recently. I have had a chronic issue of my alternator not charging my battery back up. The kit came with an aftermarket alternator, one with an SFLP connector. I have tried all combinations of connecting the wires from the connector to the old 2 wire connection on the original harness, but no luck. The voltage gauge in the car shows straight up and down, indicating no charge or drain on the battery while the engine is running, except for when my SPAL fans come on, then the gauge shows a drain until they shut off, then it goes back to neutral current. I am willing to re run new wires from the alternator, but need to know where to run them to. I know the alternator is good, i had it checked out recently. Is there something that tells the alternator to start putting out a current back to the battery, or is it always supposed to put a positive charge back to the battery? If there is any area in which i am lacking, it is electrical, does anyone have any suggestions as to how i can wire my alternator so that it will start charging the battery back up?

S - Red (Bat) If you use the red wire from the SI plug just tap it into the "S" location and run it to the "BAT" terminal along with the original "BAT" red wire.

F - Unused
L - Brown/White Gen bulb wire
P - Unused

I'm sure you have it wired correctly. Just learned this from the forum when I was going to use a serp system.

Hope it helps

Your description of the ammeter 'action' sounds like the alternator is working just fine. You would expect that the needle would be at zero if the charging system has stabilized. Does your battery go dead?

:iagree: You have an Ammeter, not a volt meter. When things are normal it's supposed to be close to straight up and down until there is a substantial load.

Here is a wiring diagram for the CS alternator plug. The brown wire may also be white in some cars, and if you don't have a GEN light in your car you can use any switched 12V source so long as it has a resistor or a light bulb inline before the alternator.

http://i106.photobucket.com/albums/m...tedDiagram.jpg

Yes it does

You need more than 12.5 Volts at the battery when the car is running. Should be putting out 14+ VDC. If the alternator is good, I would check the battery output from the alternator. Regulators are set to put out around 14.5 VDC.

I do not know the schematic of your "upgraded" system so I can't really tell you what to check for other than with a DVM at the battery.

Ok, update. I have the SFLP connector wired to my 2 wire harness like the diagram suggests, but still no luck, no charge to the battery. I then disconnected the SFLP connector, and removed the battery lead from the large stud on the alternator. I started the car, reved it once or twice, then took a volt meter while the car was running and checked all 4 of the the contacts on the sflp connector on the alternator to see if it was producing any voltage, it was not. Even when i checked the voltage of the battery stud on the alternator, still showing no DC voltage coming from the alternator. This is strange, because i watched the guys at the auto store check this alternator, and it was producing electricity. WTF???? :banghead: :banghead: :banghead:

[QUOTE=D.T.;1564124754]Regulators are set to put out around 14.5 VDC.QUOTE]

Regulators? do you mean Alternators?

[QUOTE=Bnine;1564124793]Your alternator has an internal regulator.

I am going to have the alternator rechecked again now, but in the meantime, it would help me if someone was to explain to me where physically the 2 wires from the old plug go, so i can attempt to trace them back to where they should originate, maybe there is a wire terminated somewhere it shouldnt be.

Also, another question, if i have the heavy cable connected to the battery stud on the alternator, and the alternator WAS producing approx 14VDC back to the battery, then why would the SFLP connector need to be plugged in at all?

I do not have the instructions for your "upgrade" so I cannot tell you whats what.

The 2 wires on the connector are for the feedback for the internal regulator circuit. They don't seem to be connected correctly. I would compare the new system to the old and see if they are even compatible. I assume the old system worked fine?

Did you also ground it? Sometimes they dont get a good ground through the bracket, escpecially if you painted it. The internal regulator needs a ground. There should be a threaded hole on the back of the case . I ran a good heavy ground wire from the case to the block

As mentioned above one of those wires is for feedback, but also to excite the coil and kickoff charging. A one wire alternator has a special internal kickoff circuit. The second wire on the connector is for your dash indicator 'gen' light. In summary, the red wire on the connector goes to positive ignition power(for feedback & excite), the other (brown or white) is for your dash gen indicator bulb.

If you have the large red connected to the terminal, case is grounded and at least the red connector wire hooked up to the original wiring then you do have an alternator issue.

:iagree:

Forgot that. Alt case is ground (for regulator and rectifier bridge) so it needs to be connected to the battery negative terminal. You can check it with an ohm meter. But I would make sure no paint is isolating the case from ground. Rust also. File ground connections and use dielectric grease on all connections! :flag:

Ok fellas, Im totally out of ideas.

This is what i do know:
1) On a test unit at the store, the alternator is pushing out 14.5 to 15 VDC
2) I have a clean ground from the alternator case to the block
3) The only chassis harness wire connected to the SLFP connector is connected to the "S" connection on the connector pigtail, and when the key is in the ign position, it has the same reading on it as does the battery as checked at the terminals, so battery power is being supplied to the "S" connector of the alternator in ign position.
4) I even ran a temporary separate ground wire from the alternator case directly to the negative terminal of the battery.

Even with all of this in place, when the car is running, the volts DC reading at both the stud on the back of the alternator and the battery itself is 12.25 VDC, which tells me that the battery is not being charged. Is there anything i am missing?

Your missing the L connection. It is the Field Exciter circuit and comes from the ground side of the GEN light. The other side of the GEN light has battery voltage on it.
To test it, find the white wire in the harness, check it for voltage and it should read slightly under the battery voltage. Ground it and the GEN light should come on bright. If not your missing something. If it does light, connect it to the L terminal and you should be good to go

Is it possible that I dont have a GEN light at all in this 71? I have never seen it on, and cant even find where it would be on the dash. I did however ground the other chassis wire, the one that i disconnected from the sflp connector, the one that i would have connected to the "L", but no change.

do the following to check what you've got
 

I'm assuming you got a CS-130 or CS-144

"If you are unsure which adapter to use, measure the resistance of the exciter line. Disconnect the positive battery cable and the alternator plug. Connect an ohm meter between the #1 terminal on the plug end of the alternator harness and the end of the positive battery cable. Turn the ignition key to the "on" position and read the ohmmeter. If resistance is less than 35 ohms, use adapter #8078. If it’s between 35-350 ohms, use #8077. If it’s more than 350 ohms, you have excessive resistance somewhere in that circuit which needs to be repaired, first."

...the above text is from:
http://www.idavette.net/hib/reman.html

that's the guidelines I used to wire mine in and it worked from the get-go.

In your first post, you mentioned that you tried all the possible combinations of the plug wiring in order to get it working. It is very possible that one of your first 'trials' blew the rectifiers in the alternator because it was not connected correctly. Return the alternator to the store and have them check it again. My bet is that it is now BAD. Make sure you have the wiring CORRECT before installing the next one.

No dice yet?? Geez! :willy:

:rofl:

I like that first smiley.

Anyway, your battery light should work on the dash. Unequal voltages to and from the battery/alternator mean the light comes on. I would work on getting the dash battery idiot light fixed first. If you don't have one, well you better know 4 sure. Looks like you need to study a little harder. So far you are getting a C- grade on your troubleshooting skills...

Info on the CS...

http://www.alternatorparts.com/cs130_sbpage3.htm

Well thank you all for your advice, Im going to leave this one the pro's i guess. I think this thread has run its course, you were all a great help. You all have given great input, thank you so much.

I would like however to respond to D.T. If I knew i was going to be graded, I would have studied real hard before asking for advice from you. Even though you still refer to the battery light on the dash that I dont have, and to check the alternator again although i already did twice, must have missed that one too earlier on in the post. Ill in return give him the same grade he gave me, a C- in front of everyone for his review of the thread. I personally would have sent a PM. :thumbs: I like THAT smiley :lol:

This is how they test the alternator on the bench. You need this resistance in the "L" connector to the battery. The link I gave you in my last post explains it on the last page. If this circiut is open, I don't think the alternator will charge at all. You also have to test for both voltage and amperage output, it must be within 15 amps of rated output to test good.

Who are the "pros" you mention that you are going to bring it to? I wouldn't give up and keep trying to fix it yourself. The costs of the specialized tools you buy and the experience are better spent on yourself rather than the "pros" in my opinion. :D

No LIGHT in the 71 dash, just ammeter.
Regards,
Alan

You said your battery goes dead..... have you ever cut open a battery cable that runs under a car for years and years? Even if it looks fine i have seen them so corroded and white filled, i have know idea how they even worked.....

If this were the case, wouldn't he have problems starting it? But, it could be the problem. 35 years on a OE cable that's about 15 feet long? Could be. I will say it again, use dielectric grease on ALL electrical connections. Since I have used grease I have reduced corrosion problems to zero. Hot and burned connections indicate excessive current/resistance. Undersized conductors, etc..

Could be the OE ground (neg) cable also. Since the vette uses a non metallic body, old rusty ground connections to the FRAME go bad as well. Since the car is 37 years old.

We are all helping him troubleshoot, including you. So I guess we all get your same grade.

Ahh, man. :leaving: OK, I get a C- also. I just want the guy to fix it himself. I hate bringing my vehicles to the "pros". I think we are all pros here at this site. I'll keep trying if Bnine will...

I have received MUCH GREAT information on these internet forums over the years about how to fix it yourself and repair problems. The "real" problems and solutions seem to come up. Face to face sometimes people won't tell you the real story related to their own personal agenda. Hopefully I can help others as some have helped me. :flag:

:iagree: I made a test stand for alternators and without the Field Exciter- small light and until I added the small light all the alternators I checked were bad until I added the small bulb.

The old corvettes used an ammeter instead of a voltmeter. Usually when I see a voltmeter going below 12VDC, something is wrong with the alternator or the battery. I haven't seen an ammeter in modern use at all lately.

Now with the ammeter, how do you know something is wrong? It measures the current difference between the alternator output and battery positive terminal. It should go down when you turn on the key and spin the starter, then come back up just past "0" when running?

Seems just like the same operating deal as a battery light in modern vehicles. When you turn the ign on, the battery light comes on, and goes out when you start the vehicle (if current is equal in both directions).

Bnine said in his first post that the ammeter was at "0" or no current difference in either direction, to and from the battery/alternator. Like mentioned earlier, your battery should be charging. It should stay below 0 if the alternator was bad.

Ever thought of testing the battery? If it never gets charged, how can you use it Bnine? Do you put it on an external power supply for a recharge every time you drive it?

Here is something to try, since your car does not have an alt or gen light, start it up and make sure there is power to the batt wire which you have said it does. Make sure there is power to the s wire and then momentarily apply power to the L terminal, it should then charge until you turn the engine off. That will tell you if you alternator and internal regulator are good. Once the alternator begins to charge there will be power at the L terminal even with that wire disconnected. I believe it will read about half of the battery voltage. I am not sure if you can leave full ign switched voltage to the L terminal, perhaps someone will chime in.

I was told to use a resistor or a light bulb to the L (switched) wire, not full voltage.

full voltage will work for his testing purposes

I had the same problem I also have what you added and changed out my gauges had to add a bulb to the excite wire and all is good you can mount it where ever you like.The bulb excites the alternator at start up and idle if you rev it up fairly high it usually will start charging with out the bulb the bulb wakes it up at start up while it idles.