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Discussion Starter #1
My problem is that the alternator is not charging the battery. I started the car after months of storage and the battery worked fine. But now the alternator will not charge the battery. I swapped the alternator and regulator from my other car (identical system) and the car still does not charge. The alternators are both externally regulated. I tried the debugging method below with no success. The voltages were checked with the regulator installed. Does the regulator need to be disconnected for the tests below? Also, does it matter that the gen. light is burned out? Could this cause a problem? It seems to me that if the light is burned out, current cannot flow through the system and maybe this prevents the contacts in the regulator from turning on?


Originally Posted by Peter F
I dug this out from before, hopefully it help. If not, just post or send me your questions.

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

The regulator 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 regulator #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 points.

When the battery voltage goes above a set level, the F terminal is disconnected from the battery power by the points I kept mentioning. Then the voltage drops and the points 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 or #1 terminal (field) - KOEO = #4 slight voltage, KOER = 9-12V typically
#2 terminal (sense) - KOEO = 0V, KOER = >3.2V
#3 terminal (Battery) - KOEO = 12V, KOER = 12V
#4 terminal (light) - KOEO = F slight voltage, KOER = 12V

By 12V above I mean battery voltage, which may be 12V when engine is off but could be up to 14.5V when engine is running.

Check the light: Ground the brown #4 terminal wire at the regulator. When grounded the light should come on. If you don't have a light then skip this test. Test this with the connector off the regulator.

Checking the alternator: Jumper the blue wire F terminal to the battery post on the back. This should make it easily crank out 16+ volts. Next, connect a troublelight between the battery post and the F terminal. The light should come on and you should measure > 3.2V at the other alternator terminal. If it passes these tests, then it's in the regulator or wiring.

Checking the wiring: At the regulator connector jumper the brown light wire (#4) to the F terminal (#1) and you should be able to measure >3.2 volts on the other alternator terminal or terminal #2 of the regulator connector. If these tests pass, it is in your regulator.

When doing these tests, make sure you turn off or pull the fuses for any added electronics that you can. The alternator test can produce enough voltage to damage stuff.

Peter

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There is another checking procedure in the electrical basics sticky, it's similar, but more detailed, and some of the voltage readings that I got were different than listed above.

Jumpering the F terminal to power will make the alternator charge full bore, if it is able to. Car running, you should read a very high voltage, 16-20 volts.

Often, the problem in these alternator is a bad diode. (or more than one) Since there are 6 diodes in the alternmator, it will still charge (but not at full output) with even several blown (open) diodes. Shorted diodes will cause both reduced output and a constant battery drain.

The testers in autoparts stores should catch a shorted diode, but they often do not catch an open one.

Many problems with this system get tracked back to bad connections, corresion on the terminals that give a high resistance connection.

The factory wiring harness has a bypass resister in parallel with the GEN light, the charging system will still work with a burned out bulb.
 

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Discussion Starter #3
Jim,

Unfortunately, I didn't see another procedure. Where would it be?

I jumpered the F terminal to the power and the alternator did start charging at a high rate (greater than 15V).

I suspect that a bad connection may be my problem.

Are the tests to be done with the regulator connected or disconnected?

Thanks.
There is another checking procedure in the electrical basics sticky, it's similar, but more detailed, and some of the voltage readings that I got were different than listed above.

Jumpering the F terminal to power will make the alternator charge full bore, if it is able to. Car running, you should read a very high voltage, 16-20 volts.

Often, the problem in these alternator is a bad diode. (or more than one) Since there are 6 diodes in the alternmator, it will still charge (but not at full output) with even several blown (open) diodes. Shorted diodes will cause both reduced output and a constant battery drain.

The testers in autoparts stores should catch a shorted diode, but they often do not catch an open one.

Many problems with this system get tracked back to bad connections, corresion on the terminals that give a high resistance connection.

The factory wiring harness has a bypass resister in parallel with the GEN light, the charging system will still work with a burned out bulb.
 

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Discussion Starter #4
I think that I found the problem. As I suspected, I believe that it was a bad connection. I took the 4 wires out of the connector and individually attached them to the regulator and the system now charges. The metal connections are corroding and need to be cleaned up.
 

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Alcohol, isopropyl, is best, rubbing will do, and a wire brush will clean the terminals.
Also do the horn relay buss bar. In fact, join the two red wires together on one screw.
 
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