Engine Question on 3G Alternator.
- Thread starter James.Little
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gearheadboy
15 Year Member
Ah that helped thanks! So it turns out if I leave the OEM charge wires, I don't need to connect the yellow wire to the positive post on the alt. However, where does the green one run off to?
Exile
Active Member
About half way down in this link below is one of the more better/detailed 3G alternator install diagrams that I have found.
http://www.stangnet.com/mustang-forums/threads/3g-alternator-install-a-how-to.646825/
This one: http://www.mustangcentral.net/tech/alternator.html ?
Also I have a piece of paper that came with it that says: "This alternator does not charge the battery, but maintains it." All alternators do that right, or did I grab the wrong one?
Also I have a piece of paper that came with it that says: "This alternator does not charge the battery, but maintains it." All alternators do that right, or did I grab the wrong one?
David Pepiton
Active Member
that is correct they only provide a maintenance charge to the alternator but could fully charge a battery if the conditions are right. ie long drive or high RPMs
David Pepiton
Active Member
correct that would cause issues with the voltage regulator over long periods of time.
David Pepiton
Active Member
yes the standard alternator is hardly enough amperage for the stock system especially since fuel injection.
is you have any questions text me frank
is you have any questions text me frank
Electric fan = 3G alternator if you want long life & reliability from your car.
The electric fan saves some HP. The stock fan's parasitic drag runs from 7-12 HP depending on who you talk to. The electric fan uses about 1/2 HP of power from the electrical system.
Figure this:
Ignition system & computer = 12 amps
Fuel pump = 12 amps
Exterior lights = 15 amps
Fan (heater or A/C) = 15 amps (can run between 5-25 amps depending on setting)
Radio & instruments = 10 amps
Wipers = 10 amps
That's grand total of 74 amps from a 65 amp alternator. Talk about overdrawn at the bank!
The electric fan saves some HP. The stock fan's parasitic drag runs from 7-12 HP depending on who you talk to. The electric fan uses about 1/2 HP of power from the electrical system.
Figure this:
Ignition system & computer = 12 amps
Fuel pump = 12 amps
Exterior lights = 15 amps
Fan (heater or A/C) = 15 amps (can run between 5-25 amps depending on setting)
Radio & instruments = 10 amps
Wipers = 10 amps
That's grand total of 74 amps from a 65 amp alternator. Talk about overdrawn at the bank!
Yes, I was driving the other day in the rain. I had my wipers, heater, lights and stereo going. I wasn't paying attention to my battery meter, until my stereo kicked off and the needle was in the red. When I finally arrived home the battery had enough juice to start the car one more time, then I had to hook up the battery charger. I was so glad I had my 3G waiting at the house for the install.
Speaking of, I do have the 3g installed (see attached photo). I ran a 4 AWG wire from the positive post on the alternator to a 200A fuse then to the positive side of the starter solenoide. Then I attached the green wire from the original harness to the provided green wire that came with the alternator, which I also did with the yellow wire (See original photo). From the old second harness that seem to be the output wires (two thick black and orange wires and one white). I just disconnected the wires and left them hanging around just in case.
Now, everything seemed fine, but the needle keeps moving slightly up and down, very suddle, is that normal? Also when I turn on something electrical, like the heater blower, it drops for a half a second then bumps back up to its original spot, also the lights dim for a slight second when I do that as well. Does this seem normal to everyone? Should I connect the black and orange wires to the battery post on the alternator?
Thanks for the help guys!
P.S. I have a few more pics of the install if anyone is interested.
Speaking of, I do have the 3g installed (see attached photo). I ran a 4 AWG wire from the positive post on the alternator to a 200A fuse then to the positive side of the starter solenoide. Then I attached the green wire from the original harness to the provided green wire that came with the alternator, which I also did with the yellow wire (See original photo). From the old second harness that seem to be the output wires (two thick black and orange wires and one white). I just disconnected the wires and left them hanging around just in case.
Now, everything seemed fine, but the needle keeps moving slightly up and down, very suddle, is that normal? Also when I turn on something electrical, like the heater blower, it drops for a half a second then bumps back up to its original spot, also the lights dim for a slight second when I do that as well. Does this seem normal to everyone? Should I connect the black and orange wires to the battery post on the alternator?
Thanks for the help guys!
P.S. I have a few more pics of the install if anyone is interested.
Attachments
Have you checked ripple current?
There's no need to reinstall those two original charge wires. Do insulate them since they are still connected to the battery.
Did you connect the little white wire back to the altenator the wire thats on the same plug as the black and orange wires
Edit: saw the original photo and saw that you had it hooked up already
Edit: saw the original photo and saw that you had it hooked up already
I will have to mess with it when I have some time, but I made a short video of what is happening. Also when I was driving home, before the video was made, the car just shut off on it's own. I am unsure if that is related or not.
Under no circumstances connect the two 10 gauge black/white wires to the 3G alternator. If the fuse blows in the 4 gauge wire, the two 10 gauge wires will be overloaded to the point of catching fire and burning up the wiring harness.
Here is the reasoning behind using only a single 4 gauge fused power feed to the alternator. If you use the two 10 gauge black/orange wires in addition to the 4 gauge wire, you have two fused power feed paths. The total current capacity of the wiring is the sum of the fused paths. The 4 gauge path is fused for 125 amps, and the two 10 gages wires are fused for 60 amps. That is a total of 185 amps, which exceeds the capacity of the alternator. Overload can occur without the fuses blowing, damaging the alternator.
The worst case scenario is that the alternator develops an internal short to ground resulting in a catastrophic failure. The initial short circuit surge current is limited by the resistance of the wiring. The current in a parallel circuit divides up according to the resistance of the branches. If the 4 gauge fuse opens up first, the two 10 gauge black/orange wires will be carrying the short circuit surge current. Depending on the time lag of the fuse links, they may open up before a fire starts or they may not.
The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges. Any car that has a 3G alternator needs a 4 gauge ground wire running from the block to the chassis ground where the battery pigtail ground connects.
Alternator wiring.
Starter solenoid wiring 86-91 model cars.
Connect the fused 4 gauge wire to the alternator and the battery side of the starter solenoid.
Starter solenoid wiring 92-93 Model cars.
Alternator troubleshooting for 86-93 5.0 Mustangs:
Never, never disconnect an alternator from the battery with the engine running. The resulting voltage spike can damage the car's electronics including the alternator.
Revised 15 April 2012 to add simple check for regulator failure in Engine off ignition on, battery fully charged section, item 2.
Do all of these tests in sequence. Do not skip around. The results of each test depend on the results of the previous tests for correct interpretation.
Simple first step: Remove the alternator and take it to your local auto parts store. They can bench test it for free.
Engine off, ignition off, battery fully charged.
1.) Look for 12 volts at the alternator output. No 12 volts and the dark green fuse link between the orange/black wires and the battery side of the starter solenoid has open circuited.
3G alternator: Look for 12 volts at the stud on the back of the alternator where the 4 gauge power feed wire is bolted.
No voltage and the fuse for the 4 gauge power feed wire is open or there are some loose connections.
2.) Look for 12 volts on the yellow/white wire that is the power feed to the regulator. No 12 volts, and the fuse link for the yellow/white wire has open circuited.
Engine off, ignition on, battery fully charged:
1.) Alternator warning light should glow. No glow, bulb has burned out or there is a break in the wiring between the regulator plug and the dash. The warning light supplies an exciter voltage that tells the regulator to turn on. There is a 500 ohm resistor in parallel with the warning light so that if the bulb burns out, the regulator still gets the exciter voltage.
Disconnect the D connector with the 3 wires (yellow/white, white/black and green/red) from the voltage regulator.
Measure the voltage on the Lt green/red wire. It should be 12 volts. No 12 volts and the wire is broken, or the 500 ohm resistor and dash indicator lamp are bad. If the 12 volts is missing, replace the warning lamp. If after replacing the warning lamp, the test fails again, the wiring between the warning lamp and the alternator is faulty. The warning lamp circuit is part of the instrument panel and contains some connectors that may cause problems.
2.) Reconnect the D plug to the alternator
Probe the green/red wire from the rear of the connector and use the battery negative post as a ground. You should see 2.4-2.6 volts. No voltage and the previous tests passed, you have a failed voltage regulator. This is an actual measurement taken from a car with a working electrical system. If you see full or almost full12 volts, the regulator has failed.
Engine on, Ignition on, battery fully charged:
Probe the green/red wire from the rear of the connector and use the battery negative post as a ground. You should see battery voltage minus .25 to 1.0 volt. If the battery measured across the battery is 15.25 volts, you should see 14.50 volts
Familiarize yourself with the following application note from Fluke: See http://assets.fluke.com/appnotes/automotive/beatbook.pdf for help for help troubleshooting voltage drops across connections and components. .
You will need to do some voltage drop testing of several of the wires.
Start looking for these things:
1.) Bad diode(s) in the alternator - one or more diodes have open circuited and are causing the voltage to drop off as load increases. Remove the alternator and bench test it to confirm or deny this as being the problem.
2.) The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges. Do the voltage drop test as shown in the Fluke tech note link. Measure the voltage drop between the alternator frame and the battery negative post. Watch for an increase in drop as the load increases. Use the Fluke voltage drop figures as guidelines for your decisions.
3.) Bad regulator that does not increase field current as load increases. Remove the alternator and bench test it to confirm or deny this as being the problem.
4.) Bad sense wire - open circuit in sense wiring or high resistance. The yellow/white wire is the voltage sense and power for the field. There is a fuse link embedded in the wiring where it connects to the black/orange wiring that can open up and cause problems. Disconnect the battery negative cable from the battery: this will keep you from making sparks when you do the next step. Then disconnect the yellow/white wire at the alternator and the green fuse link at the starter solenoid/starter relay. Measure the resistance between the alternator end of the yellow/white wire and the green fuse link: you should see less than 1 ohm. Reconnect all the wires when you have completed this step.
5.) Bad power feed wiring from the alternator. Use caution in the next step, since you will need to do it with everything powered up and the engine running. You are going to do the Fluke voltage drop tests on the power feed wiring, fuse links and associated parts. Connect one DMM lead to the battery side of the starter solenoid/starter relay. Carefully probe the backside of the black/orange wire connector where it plugs into the alternator. With the engine off, you should see very little voltage. Start the engine and increase the load on the electrical system. Watch for an increase in drop as the load increases. Use the Fluke voltage drop figures as guidelines for your decisions.
Alternator wiring circuit
Notice the green wire connects to a switched power source. The circuit contains a 500 ohm resistor in series between the switched power and the alternator. Connecting it to switched power keeps the regulator from drawing current when the engine is not running. The resistor limits the current flowing through the wire so that a fuse isn't needed if the wire shorts to ground.
Also notice the sense wire connects to the starter solenoid and it is fused. It connects to the starter solenoid so that it can "sense" the voltage drop across the output wiring from the alternator.
Here is the reasoning behind using only a single 4 gauge fused power feed to the alternator. If you use the two 10 gauge black/orange wires in addition to the 4 gauge wire, you have two fused power feed paths. The total current capacity of the wiring is the sum of the fused paths. The 4 gauge path is fused for 125 amps, and the two 10 gages wires are fused for 60 amps. That is a total of 185 amps, which exceeds the capacity of the alternator. Overload can occur without the fuses blowing, damaging the alternator.
The worst case scenario is that the alternator develops an internal short to ground resulting in a catastrophic failure. The initial short circuit surge current is limited by the resistance of the wiring. The current in a parallel circuit divides up according to the resistance of the branches. If the 4 gauge fuse opens up first, the two 10 gauge black/orange wires will be carrying the short circuit surge current. Depending on the time lag of the fuse links, they may open up before a fire starts or they may not.
The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges. Any car that has a 3G alternator needs a 4 gauge ground wire running from the block to the chassis ground where the battery pigtail ground connects.
Alternator wiring.
Starter solenoid wiring 86-91 model cars.
Connect the fused 4 gauge wire to the alternator and the battery side of the starter solenoid.
Starter solenoid wiring 92-93 Model cars.
Alternator troubleshooting for 86-93 5.0 Mustangs:
Never, never disconnect an alternator from the battery with the engine running. The resulting voltage spike can damage the car's electronics including the alternator.
Revised 15 April 2012 to add simple check for regulator failure in Engine off ignition on, battery fully charged section, item 2.
Do all of these tests in sequence. Do not skip around. The results of each test depend on the results of the previous tests for correct interpretation.
Simple first step: Remove the alternator and take it to your local auto parts store. They can bench test it for free.
Engine off, ignition off, battery fully charged.
1.) Look for 12 volts at the alternator output. No 12 volts and the dark green fuse link between the orange/black wires and the battery side of the starter solenoid has open circuited.
3G alternator: Look for 12 volts at the stud on the back of the alternator where the 4 gauge power feed wire is bolted.
No voltage and the fuse for the 4 gauge power feed wire is open or there are some loose connections.
2.) Look for 12 volts on the yellow/white wire that is the power feed to the regulator. No 12 volts, and the fuse link for the yellow/white wire has open circuited.
Engine off, ignition on, battery fully charged:
1.) Alternator warning light should glow. No glow, bulb has burned out or there is a break in the wiring between the regulator plug and the dash. The warning light supplies an exciter voltage that tells the regulator to turn on. There is a 500 ohm resistor in parallel with the warning light so that if the bulb burns out, the regulator still gets the exciter voltage.
Disconnect the D connector with the 3 wires (yellow/white, white/black and green/red) from the voltage regulator.
Measure the voltage on the Lt green/red wire. It should be 12 volts. No 12 volts and the wire is broken, or the 500 ohm resistor and dash indicator lamp are bad. If the 12 volts is missing, replace the warning lamp. If after replacing the warning lamp, the test fails again, the wiring between the warning lamp and the alternator is faulty. The warning lamp circuit is part of the instrument panel and contains some connectors that may cause problems.
2.) Reconnect the D plug to the alternator
Probe the green/red wire from the rear of the connector and use the battery negative post as a ground. You should see 2.4-2.6 volts. No voltage and the previous tests passed, you have a failed voltage regulator. This is an actual measurement taken from a car with a working electrical system. If you see full or almost full12 volts, the regulator has failed.
Engine on, Ignition on, battery fully charged:
Probe the green/red wire from the rear of the connector and use the battery negative post as a ground. You should see battery voltage minus .25 to 1.0 volt. If the battery measured across the battery is 15.25 volts, you should see 14.50 volts
Familiarize yourself with the following application note from Fluke: See http://assets.fluke.com/appnotes/automotive/beatbook.pdf for help for help troubleshooting voltage drops across connections and components. .
You will need to do some voltage drop testing of several of the wires.
Start looking for these things:
1.) Bad diode(s) in the alternator - one or more diodes have open circuited and are causing the voltage to drop off as load increases. Remove the alternator and bench test it to confirm or deny this as being the problem.
2.) The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges. Do the voltage drop test as shown in the Fluke tech note link. Measure the voltage drop between the alternator frame and the battery negative post. Watch for an increase in drop as the load increases. Use the Fluke voltage drop figures as guidelines for your decisions.
3.) Bad regulator that does not increase field current as load increases. Remove the alternator and bench test it to confirm or deny this as being the problem.
4.) Bad sense wire - open circuit in sense wiring or high resistance. The yellow/white wire is the voltage sense and power for the field. There is a fuse link embedded in the wiring where it connects to the black/orange wiring that can open up and cause problems. Disconnect the battery negative cable from the battery: this will keep you from making sparks when you do the next step. Then disconnect the yellow/white wire at the alternator and the green fuse link at the starter solenoid/starter relay. Measure the resistance between the alternator end of the yellow/white wire and the green fuse link: you should see less than 1 ohm. Reconnect all the wires when you have completed this step.
5.) Bad power feed wiring from the alternator. Use caution in the next step, since you will need to do it with everything powered up and the engine running. You are going to do the Fluke voltage drop tests on the power feed wiring, fuse links and associated parts. Connect one DMM lead to the battery side of the starter solenoid/starter relay. Carefully probe the backside of the black/orange wire connector where it plugs into the alternator. With the engine off, you should see very little voltage. Start the engine and increase the load on the electrical system. Watch for an increase in drop as the load increases. Use the Fluke voltage drop figures as guidelines for your decisions.
Alternator wiring circuit
Notice the green wire connects to a switched power source. The circuit contains a 500 ohm resistor in series between the switched power and the alternator. Connecting it to switched power keeps the regulator from drawing current when the engine is not running. The resistor limits the current flowing through the wire so that a fuse isn't needed if the wire shorts to ground.
Also notice the sense wire connects to the starter solenoid and it is fused. It connects to the starter solenoid so that it can "sense" the voltage drop across the output wiring from the alternator.
why in the other thread this is what one of the diagrams posted shows and the Op who had the same
issue as this guy claims that fixed it and no one said Anything bad about it but your diagram doesn't show the yellow wire on the 4ga wire
Exile
Active Member
Im curious to know more about this yellow wire as well, for when I did my 3G install recently I didnt read anything anywhere about moving a yellow wire, and I did not run that yellow wire to the other side with the 4G wire on mine either? When/why does one need to do this?
why in the other thread this is what one of the diagrams posted shows and the Op who had the same
issue as this guy claims that fixed it and no one said Anything bad about it but your diagram doesn't show the yellow wire on the 4ga wire
I havnt had any problems since the upgrade, however I have noticed that my volts gauge will jump back and forth between 13-14 volts when I have my blinker on. Is that normal?
The yellow-wire loop like in the picture above is sometimes utilized if the OEM charge cable AND sense wire are removed from the vehicle. If the OEM charge cable was left connected at the solenoid, the yellow wire is still sensing alternator output (and the loop is not necessary).
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