i am having problems with my battery not charging. the alternator is good. i have had the car running and i pull the negative cable off the battery and the car dies. my question is, are the 2 wires that plug into the back of the alternator suppose to have power going to them? right now i have power only going to one side. (the dark blue wire.) any help would be great

Yes only on blue, How do you know alt is good what are your voltages running I need a little more info. You are running a factory setup with ext.regulator?

running factory idito lights. gen light is very dim but if you pull the neg. battery cable and the car dies that does mean that the alternator is not working properly correct? just took in voltage reg. into auto zone to have tested and they couldn't get thier tester to work right or something. i decided to order a new one anyway seening thst my is pry original.

also have a brand new alternator on it that i had them test before i bought it.

You should never pull a battery cable to see if the charging system is working, it can blow the diodes in the alternator and damage other stuff. To check the charging system, check the voltage at the battery with the car running at a fast idle, should be 14-14.5 volts. For you problem, disconnect the plug at the voltage regulator, terminal 3 (should be a orange or red wire) should have power, test to see if it does. Post back.

yes it does orange wire does have power. have put new volt reg in and started it up. check battery and it reads only 12 volts when i was at a fast idle. have found a ground post on the back for the alternator and grounded it back to the battery. is this correct. i don't remember having it that way when before i started the restoration but it has been SO long. very confussed now.

i would also like toknowwhat is the small cylinder that is on the side ofthe voltage reg.? i have heard that it is called a condenser. what does it do?

You don't need the grd wire from the back of the alt to the battery. The alt is grounded by the mounting brackets to the engine, the engine or mounting bracket is grounded to battery through main negative battery cable.

Condensor, capacitor, is for electrical noise reduction. Do you have a good solid ground connection from the regulator to the radiator support? Some regulators have rubber insulators at the mounting points, reg needs to be grounded. Do you have a good solid ground connection from the negative battery terminal to the passenger side fender?

i have a good ground to the rad support and to the alternator bracket. yes i have a ground wire from the reg to the rad support too.

when i have the car running i have checked the white wire coming out of the alternator and there is no power there. this is a brand new alternator so i am so confused that i have starting to pull hair out of my head by the hand full!

This system will not put out at Idle you may need to bring up the RPM's to about 2500 to see the charging voltage come up.

Dumb question,but have you checked the output at the alternator bat post? New doesn't always equal good. Or so I've found anyway.

Disconnect plug at alternator and run a jumper from the "F" terminal to the BAT post. Start the car and run at 1500-2000rpm. You should get 16+ volts, measure at the alt BAT post. If not, the alternator is bad. This test just tells you if the alt works or not as the voltage is unregulated.

This was written by another member, a very good write up on how it works and how to troubleshoot a externally regulated charging system.

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