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Discussion Starter #1 (Edited)
1979 corvette ,
Ok gen light on bad alt right?
tested they said it was bad got new one light still on got another one tester broken so they just gave me a new one. same thing.
decided maybe had short in battery same thing
my sears gauge says it's charging 14 plus fine so why is the light still on and also ny the way the gauge in the car reads o wtf
 

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First thing-- check the wires where they plug into the alternator- common for one or both of them to break at the plug. Vibration kills them. I've seen countless alternators changed becasue of a broken wire.
Behind that, depending on what year, look at the choke heater fuse and relay.
 

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Ok gen light on bad alt right?
tested they said it was bad got new one light still on got another one tester broken so they just gave me a new one. same thing.
decided maybe had short in battery same thing
my sears gauge says it's charging 14 plus fine so why is the light still on and also ny the way the gauge in the car reads o wtf

In order to have the dash light go off charging voltage must exceed battery voltage. A real common problem is a broken wire at the alternator's side plug-in. The little wire. Of the two wires, the large red wire is hot all the time and the little wire is only hot when the key is turned on. The little wire is not a stranded wire. It is a solid wire that is very thin and it often breaks inside of it's outer jacket right at the plug-in. You can buy a new plug-in with 6" pig tails for about $4.50 at any parts store. Now for some basic troubleshooting. When you turn the key on the little wire gets energized and that "heats" the rotor's field. And when that happens the rotor becomes highly magnetized. You can check that by holding anything magnetic (a wrench or screwdriver) up against the rear bearing. If the rotor is energized the wrench will stick HARD to the rear bearing. If it doesn't stick then either the little wire is broken or your voltage regulator is shot. Now for checking maximum output. The voltage regulator regulates charging voltage by varying the ground of the field windings. By inserting a clean 16-penny nail into the small "D" shaped hole on the back of the case about 5/8" deep you ground the voltage regulator and that makes the alternator charge wide open..........with no voltage regulation. Which means it'll go into a full output and voltage will continue to rise (often to 16-17 volts and beyond). So only do a full output test for 3-4 seconds maximum. If your charging voltage is normal but the output is way less than it should be your rectifier is shot. If you look at the back side of the rectifier (the aluminum thing with the fins on it) you will see the 6 diodes in it..........3 positive and 3 negative diodes. If one of those 6 diodes is bad it will come un-soldered and stick to the face of the diode that is directly opposite to it. The Delco Remy alternators are very easy and cheap to repair and the parts are readily available at any auto parts store.
 

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Thanks guys i tried a new alt and battery
now it comes and goes

What "comes and goes"? Your idiot light? If it's still turning on it means your charging voltage isn't exceeding your battery voltage. When that light turns on pop the hood and hold a wrench up against the rear bearing. If the wrench doesn't stick to the bearing it means your alternator's field isn't being energized. Like I said in my post the little wire is likely broken off inside the connection. When the broken ends touch the light will go off and when they separate the light will come back on again. Replace that plug-in (less than $5) and your problem will most likely go away.
 

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Discussion Starter #7
Ok checked into the heater relay under the hood unplugged it cleaned it alittle seemed to work
so far no light thanks all!!
I really appreciater the info new problem new threaD lol:thumbsup3:
 

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In order to have the dash light go off charging voltage must exceed battery voltage. A real common problem is a broken wire at the alternator's side plug-in. The little wire. Of the two wires, the large red wire is hot all the time and the little wire is only hot when the key is turned on. The little wire is not a stranded wire. It is a solid wire that is very thin and it often breaks inside of it's outer jacket right at the plug-in. You can buy a new plug-in with 6" pig tails for about $4.50 at any parts store. Now for some basic troubleshooting. When you turn the key on the little wire gets energized and that "heats" the rotor's field. And when that happens the rotor becomes highly magnetized. You can check that by holding anything magnetic (a wrench or screwdriver) up against the rear bearing. If the rotor is energized the wrench will stick HARD to the rear bearing. If it doesn't stick then either the little wire is broken or your voltage regulator is shot. Now for checking maximum output. The voltage regulator regulates charging voltage by varying the ground of the field windings. By inserting a clean 16-penny nail into the small "D" shaped hole on the back of the case about 5/8" deep you ground the voltage regulator and that makes the alternator charge wide open..........with no voltage regulation. Which means it'll go into a full output and voltage will continue to rise (often to 16-17 volts and beyond). So only do a full output test for 3-4 seconds maximum. If your charging voltage is normal but the output is way less than it should be your rectifier is shot. If you look at the back side of the rectifier (the aluminum thing with the fins on it) you will see the 6 diodes in it..........3 positive and 3 negative diodes. If one of those 6 diodes is bad it will come un-soldered and stick to the face of the diode that is directly opposite to it. The Delco Remy alternators are very easy and cheap to repair and the parts are readily available at any auto parts store.
:thumbsup3:

Another great troubleshooting post. Great write up.
 
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