'67 Charging System Test Needed
08-28-2014, 06:21 PM
#1
Melting Slicks
Thread Starter
'67 Charging System Test Needed
Replaced the battery, VR and found bad diodes in the alternator. Stock 327. Had the original alternator rebuilt. The car is still not charging. Is test a to isolate the voltage regulator or alternator as the culprit. Does someone have a test to isolate the problem. Thanks
Last edited by jtranger; 08-28-2014 at 07:21 PM. Reason: add
08-28-2014, 09:20 PM
#2
Yes.
ALTERNATOR OUTPUT TEST
Voltmeter Method
1. Disconnect the two-terminal connector from the Alternator "F" and "R" terminals.
2. Connect a jumper wire from the Alternator "BAT" terminal to the Alternator "F" terminal. This provides a full field excitation.
3. Connect a voltmeter from the Alternator "BAT" terminal to the Alternator "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 Alternator trouble diagnosis aids (Diodes, field circuit checks, etc.)
ALTERNATOR OUTPUT TEST
Voltmeter Method
1. Disconnect the two-terminal connector from the Alternator "F" and "R" terminals.
2. Connect a jumper wire from the Alternator "BAT" terminal to the Alternator "F" terminal. This provides a full field excitation.
3. Connect a voltmeter from the Alternator "BAT" terminal to the Alternator "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 Alternator trouble diagnosis aids (Diodes, field circuit checks, etc.)
08-16-2018, 09:26 AM
#3
Burning Brakes
First off. All the comments here have been very helpful to get me where I am so far with my charging problem. Here's where that is...
(1967 C2 327) New alternator and battery. When I jump the BAT terminal to the Alternator F terminal (as suggested)… I get 14v+ off the alternator and almost 14v at the battery. Reconnect the F/R to the regulator. 12.4v off the alternator, 12.4v at the battery. I tested the F/R wires. They’re fine. Opened the regulator and the points open and close. I’m stumped.
(1967 C2 327) New alternator and battery. When I jump the BAT terminal to the Alternator F terminal (as suggested)… I get 14v+ off the alternator and almost 14v at the battery. Reconnect the F/R to the regulator. 12.4v off the alternator, 12.4v at the battery. I tested the F/R wires. They’re fine. Opened the regulator and the points open and close. I’m stumped.
08-16-2018, 09:43 AM
#4
Team Owner
If you're getting 14 volts at the battery with everything connected then the car is charging.
When you say it's not charging, do you mean that you don't get 14 volts at the battery with the alternator hooked up correctly, and car running, or is your battery gauge on the dash just not functioning correctly?
When you say it's not charging, do you mean that you don't get 14 volts at the battery with the alternator hooked up correctly, and car running, or is your battery gauge on the dash just not functioning correctly?
08-16-2018, 09:56 AM
#5
Burning Brakes
If you're getting 14 volts at the battery with everything connected then the car is charging.
When you say it's not charging, do you mean that you don't get 14 volts at the battery with the alternator hooked up correctly, and car running, or is your battery gauge on the dash just not functioning correctly?
When you say it's not charging, do you mean that you don't get 14 volts at the battery with the alternator hooked up correctly, and car running, or is your battery gauge on the dash just not functioning correctly?
08-16-2018, 10:01 AM
#6
Safety Car
Member Since: Apr 2000
Location: New York New York
Posts: 4,808
Received 1,120 Likes
on
550 Posts
2023 C2 of the Year Finalist - Unmodified
2023 C1 of the Year Finalist - Unmodified
I have an article I wrote on charging systems that might help you. Send me your email address and I will send it to you. I am on a cruise ship right now so it might be a day or two before I can send it.
Joe
Joe
08-16-2018, 10:41 AM
#7
Melting Slicks
Hmmm... if you are saying you get the same voltage at the battery with the car running and with the car off, I’d normally say you had an alternator issue. Because you tested the alternator, my guess is your VR isn’t working.
Ed
Ed
Last edited by emdoller; 08-16-2018 at 10:48 AM.
08-16-2018, 10:44 AM
#8
Le Mans Master
Question
Yes.
ALTERNATOR OUTPUT TEST
Voltmeter Method
1. Disconnect the two-terminal connector from the Alternator "F" and "R" terminals.
2. Connect a jumper wire from the Alternator "BAT" terminal to the Alternator "F" terminal. This provides a full field excitation.
3. Connect a voltmeter from the Alternator "BAT" terminal to the Alternator "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 Alternator trouble diagnosis aids (Diodes, field circuit checks, etc.)
ALTERNATOR OUTPUT TEST
Voltmeter Method
1. Disconnect the two-terminal connector from the Alternator "F" and "R" terminals.
2. Connect a jumper wire from the Alternator "BAT" terminal to the Alternator "F" terminal. This provides a full field excitation.
3. Connect a voltmeter from the Alternator "BAT" terminal to the Alternator "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 Alternator trouble diagnosis aids (Diodes, field circuit checks, etc.)
Thanks
08-16-2018, 01:36 PM
#9
Drifting
To my knowledge, the charging system is the same for all C2s. If I was in gjhinc's situation, I would go to Autozone and drop a few bucks on an electronic voltage regulator, plug that in, and see if it makes a difference.
The following users liked this post:
Vette5311 (08-17-2018)
08-16-2018, 02:46 PM
#10
Drifting
Here's a test method i saved from a previous post. All credit goes to the author.
Alternator Operation and Testing
By Joe Fisher
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
Page 1 of 2
http://temp.corvetteforum.net/classi...ternator.shtml 9/9/2011
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.
Alternator Operation and Testing
By Joe Fisher
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
Page 1 of 2
http://temp.corvetteforum.net/classi...ternator.shtml 9/9/2011
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.
08-19-2018, 05:43 AM
#11
Burning Brakes
Thanks Joe. That was really helpful. It least I could be sure how everything should work. Which everything did until I plugged the new voltage regulator into the new alternator connected to the new battery. Still not charging the battery unless I jump the F/BAT. I should mention that I've only own the '67 C2 for a week. So I thought I'd let the dealer (who'll remain nameless at this point) have a look. He's got a very impressive shop in the Dallas area. I went back to pick up the car yesterday morning. What I found was a total dead battery and a regulator "fix" (picture below) that made no sense. Am I missing something?
hot battery lead going into the regulator where the capacitor is always connected
04-30-2021, 03:00 PM
#12
2nd Gear
Member Since: Oct 2013
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
I’m stumped
Here's a test method i saved from a previous post. All credit goes to the author.
Alternator Operation and Testing
By Joe Fisher
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
Page 1 of 2
http://temp.corvetteforum.net/classi...ternator.shtml 9/9/2011
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.
Alternator Operation and Testing
By Joe Fisher
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
Page 1 of 2
http://temp.corvetteforum.net/classi...ternator.shtml 9/9/2011
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.
04-30-2021, 04:02 PM
#13
Administrator
Member Since: Jul 2000
Location: About 1100 miles from where I call home. Blue lives matter.
Posts: 51,357
Received 5,318 Likes
on
2,767 Posts
my 66 corvette is eating alternators. I’m on my fifth. This one has regulator built into the alternator. Is it possible that the demand exceeds the output from the alternator and the battery drains and the alternator gets fried? I have an electric fan and aftermarket ac. Car runs beautifully but only for a few days. I hate where the battery sits in the car and how the plate acts as a ground.
