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The following is specific to the 79 280 ZX, it should apply to any Nissan alternator with an Internal Voltage Regulator.

If you disconnect any wire from the Alternator DISCONNECT THE NEGATIVE BATTERY TERMINAL FIRST.

When the Ignition Switch is turned on current flows from the battery through the Brown fusible link to the "B" terminal of the Ignition Switch and out the "IGN" terminal of the Ignition Switch to the coil of the Ignition Relay, thus closing the contacts of the Ignition Relay.

When the contacts of the Ignition Relay close, current flows from the battery, through the Green fusible link connected to the Ignition Relay contacts, then to the 10 amp fuse which is connected to the "Charge Warning Lamp" in the Volt Meter, then to the "L" terminal of the Alternator. At the same time current passes through the coil of the Check Relay which is hooked in parallel with the "Charge Warning Lamp".

When current arrives at the "L" terminal of the Alternator it flows through a transistor in the IC Voltage Regulator to ground thus turning on the "Charge Warning Lamp" and "Excites" the Rotor Coil in the Alternator.

When the Alternator begins to operate, three-phase alternating current is inducted in the stator coil in the Alternator. This alternating current is rectified by the positive and negative silicone diodes in the IC Voltage Rectifier.

When the voltage at terminal "B" is higher than the voltage through the Black fusible link to the positive terminal of the battery, current produced at the stator flows to recharge the battery. While the battery is being re-charged, the voltage at terminal "L" is equal to that of terminal "B". At this point, there is no voltage differential on either side of the "Charge Warning Lamp", which causes the "Charge Warning Lamp" to turn off. Accordingly, current flow through the Rotor is taken over by the current produced by the Stator. The circuit between terminal "F" of the Alternator and the Transistor in the IC Voltage Regulator is then closed. NOTE. Terminal "F" is inside the Alternator, it eventually end up being connected to terminal "E".

The IC Voltage Regulator monitors generating voltage to be applied to the battery at terminal "S". When current exceeds a specific value it then flows through a Zener Diode, closing a circuit between a third transistor and a resistor . At this point, current neither flows through the first transistor to ground or to the Rotor, thereby reducing the voltage generated at the Stator.

When voltage generated at terminal "S" is reduced to a specific value the transistor allows current to flow through the Rotor, increasing the generating voltage.

In this manner, output voltage from the Alternator does not rise above the specified value by the ON - OFF operation of the Rotor Coil through the IC Voltage Regulator.

What to do when your charging system malfunctions.

1st. Check the battery voltage, it should be at least 12.5 V. If it is 2 or more volts less you have either a short in a cell or a seriously discharged battery. Recharge the battery. If you can not get it within specification replace it.

2nd. Check the tension of the Alternator Belt.

3rd. Check all the Fusible Links. Remove them, clean the contacts and test them with an ohm meter. They should have 0 ohms resistance.

4th. Check the 10 amp fuse. Remove it, clean the contacts and test the fuse with an ohm meter. It should have 0 ohms resistance.

5th. Check that the "Charge Warning Lamp" AND the Check Relay are both functional. If both of these are not working the "L" terminal of the Alternator will not allow the charging cycle to start.

6th. Check that the terminal "E" of the Alternator has a wire connected to a clean engine ground.

7th. DISCONNECT THE NEGATIVE BATTERY TERMINAL. Hook an automotive amp meter to the alternator "B" wire and then hook the other terminal of the amp meter to the alternator "B" terminal using 10 gauge wire with terminals on each end. RECONNECT THE NEGATIVE BATTERY TERMINAL. Check the current output of the Alternator. Is it within specification? The OEM Alternator should not produce more that 60 amps @ 5000 RPM. The voltage should not exceed 14.4 to 15.0 volts.

8th. Verify that the voltage at the "B" terminal of the Alternator is the same as the voltage directly at the battery terminals. If it is different you probably have dirty or loose connections.

9th. Verify that the voltage at the "S" terminal of the Alternator is the same as the voltage directly at the battery terminals. If it is different you probably have dirty or loose connections.

10th. Verify that the voltage at the "L" terminal of the Alternator is the same as the voltage directly at the battery terminals. If it is different you probably have dirty or loose connections. Note, that this circuit goes through the Ignition Relay and that the contacts in the relay can create a resistance if they are dirty, this resistance can affect the charging system.

11th. Under the plastic flap, beside the battery, is the horn relay, the main EFI relay and a large gauge wire in a white plactic connector. This wire comes from the alternator and feeds the fusible links. Check each connector for corrosion and clean them up.

12th. If you find that you have to remove the Alternator because you feel it is defective after conducting the above tests DISCONNECT THE NEGATIVE BATTERY TERMINAL FIRST. Once the Alternator has been removed have it tested at the place you intend to get a replacement. If they claim that your unit is OK go back and recheck your wiring.

Note, that the most common thing to fail in an alternator is the brushes get worn or the springs get weak. If the slip rings are not damaged or too badly worn it should cost about $10.00 CDN for a replacement set of brushes and springs.

Well that is about it for Charging 101, hope it helps someone out there that does not have a Factory Service Manual.



Post Edited (Sep 9, 5:28am)
 

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Great post!!!!!!
 

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Take a look above...

"Alternators, Regulators, & Z's--OH MY!"
I still can't figure out how the charge light on my 76 280 light was "on" when the wrong alternator was installed, even though it was properly charging the battery...
 

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Discussion Starter #4
Re: Take a look above...

I can not tell if you "Agree" or "Disagree" with my post. LOL

I did say it was for a 79 280 ZX and AFAIK the 76 had an external voltage regulator so it would probably not be completely applicable to your vehicle.

Wayne Monteath
Masham, Quebec.
 

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Re: Take a look above...

Doesn't apply to me, but great post. This is the sort of gold Z info that we all love to see. Good on ya

Loops
 

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Another saved post...........Im sure I will be needing in future,
thanks Wayne...........great write up.

Charles
 

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Thanks for the info. If is not raining tomorrow I will check it out.
 
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