need info on broken plug wire on alternator - Team Camaro Tech
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post #1 of 5 (permalink) Old May 24th, 06, 05:02 AM Thread Starter
 
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need info on broken plug wire on alternator

Hi
I have a 3 wire alternator on my big block. The black two wire plug that plugs into the alternator, I found that one of the wires was broken and no longer connected to the plug. I hope to fix it this weekend.
Question is
What does the two wired plug control AND what problems would I have had if I didnt notice it was broken ?

P.S. My Autometer guage read that it was charging at 13 volts with the broken wire. I also would prefer to stay with a 3 wire alternator.

Thanks
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post #2 of 5 (permalink) Old May 24th, 06, 05:33 AM
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Re: need info on broken plug wire on alternator

Quote:
Originally Posted by jaytone
Hi
I have a 3 wire alternator on my big block. The black two wire plug that plugs into the alternator, I found that one of the wires was broken and no longer connected to the plug. I hope to fix it this weekend.
Question is
What does the two wired plug control AND what problems would I have had if I didnt notice it was broken ?
Yr of car? Does the alternator have a external or internal regulator? Which terminal? (in relation to the BAT terminal where heavy red goes) Problems could be alt not charging or if the wire touched ground, a short
Quote:
Originally Posted by jaytone
P.S. My Autometer guage read that it was charging at 13 volts with the broken wire. I also would prefer to stay with a 3 wire alternator.
Thanks
Was it lower than normal.

Greg U

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post #3 of 5 (permalink) Old May 24th, 06, 05:56 AM
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Re: need info on broken plug wire on alternator

I have found identical bare terminals at Napa. It took some looking thru the old printed catalog to find them. and I'm afraid I didn't archive the part number.

You can also find a replacement connector with pigtails in the help department of most autoparts stores, just peel back the tape, splice it in and rewrap the harness.





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post #4 of 5 (permalink) Old May 24th, 06, 06:26 AM Thread Starter
 
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Re: need info on broken plug wire on alternator

Quote:
Originally Posted by undee72Z
Yr of car? Does the alternator have a external or internal regulator? Which terminal? (in relation to the BAT terminal where heavy red goes) Problems could be alt not charging or if the wire touched ground, a short

Was it lower than normal.
The car is a 1970 Nova with an external voltage regulator. It is a yellow wire that is on the right side of the plug. It did appear to be charging somewhat lower than normal. Before it was broken the Autometer gauge needle read 14volts and after it broke, it read 13 volts
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post #5 of 5 (permalink) Old May 25th, 06, 04:10 AM
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Re: need info on broken plug wire on alternator

Voltage is low on that wire. With it broken, low or no output would be the result. Heres more info on external charging systems.....

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

Greg U

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