79 Vette Alternator Problem
Thread Starter
8th Gear
Joined: Mar 2011
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79 Vette Alternator Problem
My car suddenly developed a short in the wiring from the alternator to the starter. I have tried a direct jumper from the back connection direct to the starter same short. The red and brown wire seem to be ok. The brown one hot with key on and red always hot. It only throws this short while running although the back connection is always hot. I first noticed this problem when the tach pegged out. It stays pegged. The alternator tested good but replaced it anyway.Can someone out there help this thing has me baffled.
Race Director
Joined: Sep 2004
Posts: 11,874
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
lets make sure our terminology is the same....short means that you have a direct connection to ground and fuses blow and wires burn up...
open means there is no connection between wires like you took a good wire connection and then cut the wire in half and broke the connection.
so which do you have?
open means there is no connection between wires like you took a good wire connection and then cut the wire in half and broke the connection.
so which do you have?
Thread Starter
8th Gear
Joined: Mar 2011
Posts: 8
Likes: 0
lets make sure our terminology is the same....short means that you have a direct connection to ground and fuses blow and wires burn up...
open means there is no connection between wires like you took a good wire connection and then cut the wire in half and broke the connection.
so which do you have?
open means there is no connection between wires like you took a good wire connection and then cut the wire in half and broke the connection.
so which do you have?
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
almost makes me think the sensing wire that tells the alternator how much juice to put out is not giving the proper feed back and the alternator is putting out too much juice to overcompensate for it....did any body do any fooling around under the dash?
or less likely but is floating around in mind....i wonder if you have a situation where you do have something shorting out requiring all the extra juice....although i would think the smoke would start escaping from some wires
or less likely but is floating around in mind....i wonder if you have a situation where you do have something shorting out requiring all the extra juice....although i would think the smoke would start escaping from some wires
Thread Starter
8th Gear
Joined: Mar 2011
Posts: 8
Likes: 0
almost makes me think the sensing wire that tells the alternator how much juice to put out is not giving the proper feed back and the alternator is putting out too much juice to overcompensate for it....did any body do any fooling around under the dash?
or less likely but is floating around in mind....i wonder if you have a situation where you do have something shorting out requiring all the extra juice....although i would think the smoke would start escaping from some wires
or less likely but is floating around in mind....i wonder if you have a situation where you do have something shorting out requiring all the extra juice....although i would think the smoke would start escaping from some wires
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
this is going from memory......go to madelectrical 101 and read about the 3 wire alternator......thats what we have....one of those wires from the back of the alternator goes to the fuse panel or a main connection and senses the voltage....it then gives this back information back to the alternator and it cahnges its output accordingly....i suppose if you figure out which wire it was you could put a jumper between your alternator out put lead and the incoming sensing wire and see it that changes anything....the idea is that the sensing wire for some reason is getting a low voltage and asking the alternator to produce more and trying to charge a fully charged battery is creating the problem
as for the problem only happening when its running that makes me think its load related
heres another idea....i should have thought of this before.....lets start pulling fuses and see if that fixes the problem? pull them all and then put them back in one by one and check the amperage on each to make sure its correct.
as for the problem only happening when its running that makes me think its load related
heres another idea....i should have thought of this before.....lets start pulling fuses and see if that fixes the problem? pull them all and then put them back in one by one and check the amperage on each to make sure its correct.
Last edited by bobs77vet; Jul 4, 2011 at 01:27 PM.
