[IROCJOE]

I am having a charging problem with my 68 SS396. When the engine is running the voltmeter is running around 11.8 volts. When the blinkers go on (or anything for that matter) the gauge dips below that. I've replaced the alternator, horn relay, voltage regulator, battery cables and various old wires. The battery holds a charge and starts the car just fine as long as I don't run the headlights or take long drives. I've searched and read many messages on this forum and ran some of the tests. Here are the results:

1. Removed the plug from the regulator and turned ignition on and engine off. Measured the brown wire to a ground and had 12.75 volts.

2. Put connector back on and removed plug from alternator. With key on and engine off, the blue wire to a ground showed 12.35 volts.

These tests were done with key on and engine off at the voltage regulator:

F terminal at alternator = 11.50 volts
#2 terminal = 0 volts
#3 terminal = 13.02 volts
#4 terminal = 11.5 volts

I cannot test with engine on until I replace the bendix in the starter. But I did test it awhile back and got a little under 12 volts at alternator red wire with about 1000 rpm's. I've also checked with a ohm meter the continuity of each wire and got 0 ohms which means the wires are okay? The alternator was tested a couple of times (first when bought and once I took it back) and it tested just fine on their machine. Like I said earlier, I can't do the alternator flash test until I get her to run. Does anyone have any ideas what the problem could be? The wiring seems fine and still points to the alternator not kicking on but the machine kicks it just fine!? I'm at wits end with this SOB. What can I do next????

Thanks,
Gary

 

[rusty66]

Gary. Reading your post I wonder:

- The shop test shows the alternator is working properly. They are NOT using your regulator, could this be at fault?
- The shop does not use your grounds: is the alternator grounded to the engine block, is the engine block grounded properly (you say you can start, so it ought to be), is the regulator grounded?
- The battery holds charge when the load is low + the voltage at the field wire is 11.5 V. The alternator seems to be needing more for its field : is the regulator at fault?
- You replaced some old wires ? Perhaps you made a mistake ?

I do not have a wiring diagram in front of me, so I cannot comment on the other measurements. Sorry.

Hope this helps some.

Rob

 

[IROCJOE]

Rob,

The regulator is NEW. I've had this problem since I've had the car so I started replacing the obvious things trying to eliminate the problem. The alternator has another lug (below the two wire connector) that has nothing on it. Is that for a ground? Does it need it if the block is grounded and therefore the alt and alt bracket ground to the block? The block IS grounded with a ground strap and the car starts up just fine IF the battery is not low due to heavy driving. Like I said earlier, it has always had this problem and when I looked at some of the wires, they were either bad connections or bad wire. I replaced those along with the battery cables trying to rule out some of the obvious hurdles. The regulator is mounted to the radiator support with 4 screws and is metal against metal. Is that enough ground? Anyway to test the regulator? I know it is new but could still be bad. Where can I go from here????

 

[IROCJOE]

Any ideas....please.

 

[Peter F.]

Here's my copied troubleshooting response. Once you get the thing running check it out. If you can't find it, come back here (to this post). Right now, I believe the F and #4 voltage is way too high for a engine off voltage test unless the alternator was not connected.

***

I'll try to provide a simplified explanation of how the externally regulated alternator and regulator work here. This explaination starts from a parked car with engine off state.

The brown #4 wire is connected through the light bulb to 12V whenever the key is in the ON position. The other end goes through a set of points in the regulator and then out the F terminal to the field winding in the alternator. So some current begins flowing in the field winding from this connection. The little bit of current flowing produces a weak magnet field in the alternator and also lights the bulb.

When you then start the car, the weak magnetic field from above begins rotating which makes the alternator producing a little bit of voltage. This voltage is fed from the alternator to the regulator on the white #2 wire. This wire connects to a coil in the regulator and turns on a contact when the voltage goes above 3.2V.

Once the contact turns on in the regulator the #3 and #4 terminals are connected together. Terminal #3 is battery power so this puts battery power on both sides of the bulb and turns it off. This means the brown #4 wire should go to +12V. Also, this connects the field terminal right to battery power but still going through the contact.

When the battery voltage goes above a set level, the F terminal is disconnected from the battery power by the contact I kept mentioning. Then the voltage drops and the contact close again. This on-off cycling happens rapidly and is how the voltage gets regulated.

From the above (KOEO = key on engine off and KOER = key on engine running).
F terminal - KOEO = #4 slight voltage KOER = 9-12V typically
#2 terminal - KOEO = 0V KOER = >3.2V
#3 terminal - KOEO = 12V KOER = 12V
#4 terminal - KOEO = F slight voltage KOER = 12V

By 12V above I mean battery voltage, which may be 12V when engine is off but should be 14V when engine is running.

Check the brown #4 wire by grounding it at the regulator. When grounded the light should come on. If you don't have a light then skip this test.

Jumper the blue F terminal to the battery right at the alternator connector. This should make it crank out 16+ volts. If it passes this test, jumper wire the brown wire to the same F terminal and you should be able to measure >3.2 volts on the other terminal. If these tests pass, it is in your regulator or the wiring to the regulator.

If you know for sure the wiring is good then try getting another regulator. The first one I purchased wasn't the right one but it looked correct and fit right. At least thats what the parts guy though but at any rate it was either wrong or didn't work.

Peter

 

[Didge]

IROCJOE,

Like the others have said it sounds like bad voltage regulator. I had a similar problem and I knew the regulator was bad. Smell th burning..
So I go to Autozone and buy me a new Wells electronic regulator and put it in. Start having other problems so I pull my alternator and have it checked, and it was ok. To make a long story short, went back to Autozone and they have a tester for the regulator and it was bad, brand new..

So they get me another one and I ask them to test it for me and it was good. Took home and installed. No problems since..

( knock on wood )

 

[rthlc]

Lots (most) here know much more than me but try unplugging the regulator and checking voltage at #3 terminal. It should read 12 volts, if not, that could indicate a bad fusible link in the #3 wire.

 

[IROCJOE]

Thanks guys for all your help. The problem turned out to be a bad alternator. Even though I had it tested 3 different times, it tested bad the last time. Replaced it and it now works just fine! I did get a chance to replace alot of the wiring and learn alot in the process. This board is great!!

Thanks,
Gary