Alternator/VR Problem

[wkcarson]

I searched extensively on this board, but have not seen another posting with my same "symptoms". I am hoping to get some good advice on an alternator/VR problem I am having. Here is the problem:
-I was taking my 82 930 on a drive this am when I noticed my tach was floating at 4-6K, even at idle. I drove home and shut the car down.
-The alternator warning light was NOT on.
-After shutting the car down, I tried to start it up, but the battery was too weak to turn the starter. Voltimeter showed battery to be 9.3V.
-I charged the battery for about 30 minutes to 10.5 Volts, then started the car. The alternator light never illuminated on the dash, not even at initial start up with the ignition on.
-On futher testing, the voltmeter revealled NO charging to the battery, ie, it was 10.5 volts when I started it, and it DID NOT change from this at idle, and at 3-4K RPM.... it dropped after running the car for a few minutes to 10.2.
-I checked the battery connections and transmission ground strap, all were cleaned and retightened..... no change.
-The battery is an almost new (3 months old) optima.

Obviously, I am assuming that the problem is the VR or alternator. I am a little baffled that there seems to be NO current to the battery, not even a little bit when the engine is running. It seems that the consensus is that when the VR goes bad, the voltage is too high to the battery, but I don't know if this is always the case. Also, to reiterate, the dash light DOES NOT GO ON AT ALL (it was working before, so I am assuming that it's not burned out). If anyone out there has in depth knowledge and can pin point the problem to either the VR or the alternator, please let me know. Otherwise I'll pull the alternator/VR and get them tested- probably inevitable, but just wanted your advice before doing this.
Thanks in advance, this board is always great...

WK Carson
San Diego, CA

[Early_S_Man]

WK,

Does the alternator warning lamp come on each and every time when you turn on the ignition switch? If so, then I tend to think you have worn brushes in the alternator, and brushes making no contact at speed, hence no output and the battery Voltages you noted.

If not, then the possibilities are:

1. Burned out warning lamp bulb

2. Worn-out brushes

3. Broken Blue #61 wire ... somewhere between gauge lamp holder and alternator

One of the little-known facts of the automotive world is that the warning lamp MUST come on in order for the alternator to generate any output ... your battery will soon be dead without a functioning warning lamp! The pre-excitation current for the field winding comes from the warning lamp, and without pre-excitation current, there is no Voltage induced in the stator windings!

[304065]

WK,

The starting point for all charging system diagnosis is a fully charged battery. Leave the charger on overnight, or for as many days as required, to get the battery to full charge, 12.6V.

As Warren says, if the light's not lit, you will NEVER get a charge.

At the port-side rear of your engine compartment there is a 14-pin connector for the engine wire harness. Carefully remove that connector. You will notice that it is female, and has 14 holes on the sides. A close look will reveal that the holes are numbered. Locate the pin marked #11. Now, find the corresponding MALE pin that sticks out of the back of the electrical console (the part you disconnected the connector FROM). Carefully connect a ground wire between MALE pin #11 and the chassis (I use the motor mount bolt for a ground.) Turn on the ignition, and the alternator warning lamp should glow brightly.

If it does not, you've identified the problem. If it does, the problem is in the VR or alternator. Give us a report.

Caveat: don't burn yourself or the car down, if you are not certain what to do, contact a qualified shop in your area.

[wkcarson]

Gentlemen,
Thank you so much for your replies... Warren, the alternator light on the dash never comes on. I will charge the battery fully and run the quick diagnostics as you and John recommended. I'll post the results when I'm done. Again, thank you guys very much!

-Keith

[Jim Chambers]

Only a slight "high jack": If the warning light comes on but charging is not adequate (red light is dimly on at all rpm) what is the next diagnostic step? How do I test alternator output (I have a volt/ohm meter)? Also, could the culprit be the regualtor? How do I check it? My car is a '66 so I don't think I have the 14 pin connector.

[304065]

Alternator output test: with VOM meter on DC voltage scale, measure the voltage at the battery terminals. If it's anything less than about 13.5 volts, you have alt/vr or cable issues.

Correct, the 66 does not have 14-pin connector. You can pull the alternator out of the shroud and ground the blue wire that's connected to the D+/61 terminal to the engine block with the igntion on. The warning lamp should glow brightly.

A dim glow could be a loose belt or a blown diode, or oxidized wiring. But the first thing to check is alternator output at the battery terminals with the engine running.

[Jim Chambers]

Thank you John. Will do today.

[Jim Chambers]

Well, as usual, problem appears to be operator error. After poking around with the volt meter and getting no clear indication of the problem, I got out the wiring diagram. A few weeks ago I disconnected an ammeter that PO had installed. Looking at the diagram I saw that the red/white from alternator that should connect to a black to the starter wasn't. It happens at a terminal block back near the regulator. I connected correctly and now the warning light goes completely out at rpm above idle. What I can't figure is how the car started and ran fine (until the battery finally gave out) and why the warning light was only dimly lit while driving. I would think it should have been very bright, just as when the ignition is turned on. Got the charger on now. Road test tomorrow.

[wkcarson]

John,
Not sure if you are still reading this post, but here is a quick update: when I grounded pin #11 with ignition on, the alternator light glowed brightly. No problems with the light and wiring leading up to it. New alternator and VR is on the way.... I am replacing both since I am in there now anyway and I don't have huge amounts of extra time for working on the car.
Thank you again for the help... I learned a bunch. I do most everything on the car myself (dropping engine, replacing clutch, valve adjustments, etc, etc) but electrical is not my forte! Again, many thanks-

Sincerely,
W. Keith Carson

[304065]

Keith,

Save the old stuff, when you get some time you can test it to see if it's okay, sell it here. Glad you got it figured out.