67-427ci

I am working on a friends 64 Coupe and the alternator will not charge. A rebuilt alternator & new regulator have been installed with no change. The alternator was tested when I purchased it and it is good.

I have the following information:
Battery is fully charged
Voltages were checked with the engine running

12V red wire on alt reads 12.4V
ground is connected and good
grey plug: blue wire is 11.2V, black wire is 0V

Regulator voltages (looking at the lugs from the bottom of the regulator right to left)
lug-1 11.8V blue
lug-2 0V black
lug-3 12.4V red
lug-4 (condenser connection) 5.2V pink

We had the same results with the original alternator and regulator. The old alternator was tested and it was putting out only 12.5 volts so we went with a new one.

The battery gauge does not show any discharge with lights on and engine off (or on).

I am not sure what to check next.

Thanks for your help, Roy

dkleather

Roy, Not sure if this will help but I had this testing information in my files from previous posts on the Forum on the subject months ago. Maybe you can use it to solve your problem. Good Luck. Dave

Here is a basic explanation of how an alternator/regulator works:
When you start the engine a voltage is sent to the number ‘4’ terminal of the regulator, then it goes through the regulator, out the blue wire to the ‘F’ terminal of the alternator.
This energizes the field of the rotor and creates a spinning magnetic field inside the stator windings of the alternator. This starts the charging cycle. Now a small amount of voltage is sent back out the ‘R’ terminal of the alternator (white wire) to the number ‘2’ terminal of the regulator. This closes a set of points and allows the battery voltage from the red/orange wire to power the field circuit. If you had an idiot light it would now turn off. The amount of field current depends on the electrical load that is placed on the system. Now that the stator is producing current it will maintain the battery and take care of all the loads that are put on the electrical system.
Remember the battery is there to start the car and add current to the system only when the alternator is not producing enough to cover the electrical loads.
So if you have 37 amp alternator and you have 40 amps of electrical loads, then 3 amps will be supplied from the battery. This means the alternator has no current left to charge the battery and the voltage reading across the battery will be below 12.66v.
A properly working system should maintain a battery voltage of approximately 13.8-14.8 volts depending on temperature.
Always check charging volts with a fully charged battery and engine above 1000 RPM.
If the battery is very low when tested, then the charging voltage will be low. As the battery begins to charge then the charging voltage will rise.
A fully charged battery, after any surface charge is removed, will read 12.66v.

Alternator/ regulator testing:
First, check for battery voltage at the stud where the large red or orange wire connects to the alternator. You should have battery volts. If not, repair the wire or circuit.
Then disconnect the plugs from the regulator and alternator.
Check the continuity of the blue (field) and the white (relay) wires between the plugs.
Repair any wire if they do not have continuity.
Reinstall the alternator plug and leave the regulator plug disconnected.
With a voltmeter, check voltage at the number 3 terminal on the regulator plug, it should read battery voltage. There should not be any voltage at the other three terminals at this time.
If you have voltage at the number 2 terminal, R on the alternator, you have a leaky diode in the alternator, replace the alternator. This will cause a battery drain and the regulator with be hot to the touch with the key off.
Now turn the key on, you should have voltage at the number 4 terminal, this wire comes from the fuse panel. If you had an “idiot light”, this would be from the bulb.
This is what is called the exciter circuit, without voltage to this terminal the charging system will not begin to charge.
If no faults were found so far, leave the regulator plug disconnected, make sure all wires are clear of the fan and start the engine.
With a voltmeter connected to the battery and the RPM at approximately 1000-1200, jump from the ‘F’ terminal of the regulator plug to the ‘3’ (orange or red wire) terminal.
You should see an increase in voltage at the battery and hear the alternator working. If you hear a growling noise from the alternator you have either a bad diode or a bad stator winding.
Don’t leave the jumper connected too long because you don’t want the voltage to go over 15 volts for an extended period of time.
If you don’t see the voltage go above battery voltage after a few seconds then you have a bad alternator.
If the voltage rose quickly and then decreased this means you have a slipping fan belt.
Now connect a voltmeter to the number ‘2’ terminal (white wire) of the regulator connector and again momentarily jump from ‘F’ to 3. You should see about 8-10 volts.
If not, you have a bad diode in the alternator.
If all is OK up to this point reconnect the regulator connector.
If it is still not charging, run a separate ground wire from a good ground to the base of the regulator. Now if no there is still not charging, replace the regulator.
If you have an overcharging condition, it is either a bad ground at the regulator base or a bad regulator.
This is the basic testing procedure that I have been using for many years. There are other possible problems that can cause a no charge condition but they are rare and harder to diagnose.
Any questions or comments you can email me.

67-427ci

Dave: Thanks! This great information that should help me find the answer. I'll post results as soon as I have them.
Thanks again, Roy

67-427ci

My test results are as follows:
Have battery voltage on the alt. main power stud.
Continuity tests OK between the alt plug & the reg plug. On this car they are blue & black wires, both OK.
With alt plug on & regulator plug off, have batt voltage on #3 terminal (red wire). No voltage on the other 3 terminals.
With key on have 12V on #4 terminal, pink wire (regulator plug).

Note: regulator plug wires are 1-blue, 2-black, 3-red & 4-pink. The wires had paint on them, but I think these are the colors.

Started engine with alt plug connected & jumped red (no. 3) terminal to black (no. 2). The alternator started charging.

Not sure about the next test as there is no white wire in the regulator plug.

Ran a separate ground from the regulator to battery & still no charging.

Any ideas? Roy

buns

This test removes the regulator from the circuit and will tell you if the alternator is working or not.

P.S. The 'Delcotron' is the alternator.


ALTERNATOR OUTPUT TEST
Voltmeter Method
1. Disconnect the two-terminal connector from the Delcotron "F" and "R" terminals.
2. Connect a jumper wire from the Delcotron "BAT" terminal to the Delcotron "F" terminal. This provides a full field excitation.
3. Connect a voltmeter from the Delcotron "BAT" terminal to the Delcotron "GRD" terminal.
4. Start engine and turn on high beam headlights and the high speed on the heater blower. Slowly increase engine speed to 1500 rpm or slightly above and note voltage reading obtained. A voltage of 12.5 volts or more within a few minutes indicates Delcotron output is satisfactory. Stop engine and reconnect wiring.
CAUTION: When performing Step 4, engine speed should be increased slowly to prevent the unregulated voltage from exceeding 16 volts during test. If battery is in a normal state of charge, voltage will exceed 12.5 volts as soon as engine speed is increased.
5. If voltage is less than 12.5 volts, refer to the appropriate shop manual for Delcotron trouble diagnosis aids (Diodes, field circuit checks, etc.)

dkleather

The "64 wiring diagram indicates the white wire runs from the outer most post (either 1 or 4....I don't remember which direction they're numbered) to the alternator gray plug and is in the plug with a Dark Blue. Both of the gray plug wires ....white and dark blue.... run directly to the regulator. The white going to an outer most post. Sounds from your description that your wire is black instead of white. Here's the diagram I used posted by Magic V8 at one time. http://www.corvetteforum.net/classic...iring64-65.jpg Click on the diagram to magnify what you want to see. Hope this helps. Dave

BrettG

Roy,

By chance was a new engine wire harness recently installed?
I was contacted by Lectric Limited a few weeks ago & they identified
a group of engine wire harnesses(may have been for 65 only) in which
two wires were improperly positioned.

67-427ci

The more I look at this the more confused I get. It appears this is not the original wiring harness, but it was not replaced recently. This car was purchased a few months ago and has never charged the battery.

I am starting to think the regulator plug is not wired properly. First off starting with the alternator (grey) plug looking at it from the back, the "R" wire (on the left) is blue and the "F" wire (on the right) is black. The Doc rebuild wiring diagram shows these to be blue & white and reversed. I checked my 67 and they are reversed from this. Tracing these wires (& checking continuity) to the regulator plug, the blue "F" wire goes to terminal 1 and the black "R" wire goes to terminal 2. Regardless of color, I believe the "F" wire should be on terminal 1 and the "R" wire on terminal 2. In this case the black wire is in place of the white wire. Would someone please take a look at their 64 and verify what wires are on which terminals on the regulator?

Another strange thing is the #4 terminal (pink) on the regulator has only 5.2V. If the ground is removed from the regulator it jumps to 12V. I don't know if this is normal or not or how much voltage is required to excite the circuit.

Thanks, Roy

dkleather

Roy, On my early 64 327/300 no air car the F on the alternator goes to #1 on the regulator and the R goes to #2. My colors are black and green for those two locations but they are connected as stated. Dave

buns

This diagram should help.








Note that a black/pink wire (for example) originally was a black wire with a pink stripe. An aftermarket harness may just use a pink wire.

67-427ci

Thanks Tim: That is a big help. I am going to double check the wires again this evening. According to this diagram the R & F wires are reversed at the alternator plug.
Roy

67-427ci

Tim & Dave: Thank you for you assistance. It turned out the R & F wires were reversed at the alternator grey plug. I switched them and it charges perfectly (14.7 volts). I could not have solved the problem without your help. It has been like this since the car was purchased a few months ago.
Thanks again, Roy

dkleather

Roy, Glad to be of help. I've made many files of info from this Forum over the years and it always comes in handy. It's great to have so many knowledgeable people....I'm not one....to build those files and be able to use them. Happy you've found and fixed the problem. Now go and enjoy a ride!! Dave