Alternator problems
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From: Gig Harbor, Wa
Alternator problems I had the car die on me a while back then went to restart and the battery was completely dead. I put in a fresh battery and checked the output of the alternator. I was getting around 3 volts on the alternator terminal. I figured this was bad and installed a new alternator. Now with the new one in place, I am still getting aroung 3 volts.
PS: This is a 99 F-body alternator, engine and computer.
Any suggestions?
PS: This is a 99 F-body alternator, engine and computer.
Any suggestions?
Joined: Nov 2001
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From: Anderson, Indiana
If you are talking about the output terminal, it sounds like a bad connection. The output terminal of the alternator goes directly to the battery thru a large gauge wire, so whatever voltage you read at the alt. terminal should be the same as what you read at the battery. If you read 3 volts at the alternator and 12 volts at the battery, then the connection of the wire between the two is just really bad, loose, or corroded.
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91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
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From: Gig Harbor, Wa
With the output wire disconnected, I get 12 volts on the wire leading to the battery. With the wire attached and the engine running, I am getting the 3 volts. This tells me the alternator is putting out -9v. Could this be a problem with the rectifier diodes in the alternator or the wire coming from the PCM? As I understand the "regulator" is the PCM sensing the output voltage and sending a control signal via the little red wire back to the alternator. When I get home tonight, I am going to check for continuity between the PCM and the plug on the alternator.
Joined: Nov 2001
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From: Anderson, Indiana
You may have alternator problems also, but it still sounds like a bad connection somewhere. You just can't pull a 12 volt battery down to 3 volts without some glowing wires and loads of heat; unless there is a high resistance (bad) connection somewhere or a battery with a bad cell in it.
All of the regulating is still done in the alternator. The PCM just provides the turn on, and not much else. On some applications the PCM controls the alternator "field" voltage. On those, the PCM is doing a lot more, but on our LS1's the PCM doesn't have too much to do with it.
All of the regulating is still done in the alternator. The PCM just provides the turn on, and not much else. On some applications the PCM controls the alternator "field" voltage. On those, the PCM is doing a lot more, but on our LS1's the PCM doesn't have too much to do with it.
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91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
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From: Gig Harbor, Wa
Update for those interested.
On the output of the new alternator I get 3.5V with the car running. 12V with the car off. If I disconnect the output, I get 12V on the wire (duh) and 0V on the alternator.
I have good continuity between the alternator and the + terminal of the battery and good continuity between the signal wire and the PCM.
I went to exchange the alternator and it is a special order item. How can an alternator for a 99 Camaro be a special order item?
Hopefully I will get the next new one tomorrow.
On the output of the new alternator I get 3.5V with the car running. 12V with the car off. If I disconnect the output, I get 12V on the wire (duh) and 0V on the alternator.
I have good continuity between the alternator and the + terminal of the battery and good continuity between the signal wire and the PCM.
I went to exchange the alternator and it is a special order item. How can an alternator for a 99 Camaro be a special order item?
Hopefully I will get the next new one tomorrow.
That really sounds like a bad ground between the engine block and the chassis. If I recall correctly, the alt grounds to the engine block thru its housing, and without a good ground from the engine block to the chassis you can't get the alt to build a field.
On my '01 LS1 there was a ground strap bolted near the alt, which I attached to my frame rail. I also added a big ground strap at the rear drivers side head to my car's existing firewall ground point.
Did your LS1 have a ground strap near the alt? If so, where did you attach it on the car? If not, where did you ground the engine to the chassis?
On my '01 LS1 there was a ground strap bolted near the alt, which I attached to my frame rail. I also added a big ground strap at the rear drivers side head to my car's existing firewall ground point.
Did your LS1 have a ground strap near the alt? If so, where did you attach it on the car? If not, where did you ground the engine to the chassis?
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From: Gig Harbor, Wa
Last night I replaced the alternator again and everything worked perfectly. Got 14.6V. I have two engine ground straps. One on the front passenger's side that goes directly to the frame and one near the alternator that also goes to the frame.
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From: cobourg ON
hey guys just my 2 sens' I had the same problem my charging was totally iradic and un-eplainable i took it to the local alternator shop and the guy told me the red wire was a 12 volt wire with a simple 40 OHMs resistor to turn on the voltage regulator well i did some more research and I found out the computer actually creates a ground through the red wire yes a ground regulated of cource but its a ground not a power wire hahaha dumb alternator guys but ya after finding this out i decided to take the alt off because by this point i was gettting a constant 5 volts but not 14. removed alt cleaned with brake/parts cleaner and noticed the charging pole was slightly not even real noticible but took a wrench to it and tightened it then put it back on and had a magical 14.6 volts hahaha yes bad gremlin ive been working on for 3 days and a simple vibration loosened things enouph to ruin good racing time haha but ya check that {maybe} no guaranties but i do sujest if ur alt has ever been taken off to check those charging posts guys aluminum isnt as conductive make sure there are good contacts!!!!
Originally Posted by bifster
hey guys just my 2 sens' I had the same problem my charging was totally iradic and un-eplainable i took it to the local alternator shop and the guy told me the red wire was a 12 volt wire with a simple 40 OHMs resistor to turn on the voltage regulator well i did some more research and I found out the computer actually creates a ground through the red wire yes a ground regulated of cource but its a ground not a power wire hahaha dumb alternator guys but ya after finding this out i decided to take the alt off because by this point i was gettting a constant 5 volts but not 14. removed alt cleaned with brake/parts cleaner and noticed the charging pole was slightly not even real noticible but took a wrench to it and tightened it then put it back on and had a magical 14.6 volts hahaha yes bad gremlin ive been working on for 3 days and a simple vibration loosened things enouph to ruin good racing time haha but ya check that {maybe} no guaranties but i do sujest if ur alt has ever been taken off to check those charging posts guys aluminum isnt as conductive make sure there are good contacts!!!!
the alternator turn on wire is +12v and comes from the PCM... its not a ground.
Joined: Nov 2001
Posts: 1,707
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From: Anderson, Indiana
Nope.
Here's one of the threads where I explained how to properly hook it up:
https://ls1tech.com/forums/showthrea...ght=alternator
Here's one of the threads where I explained how to properly hook it up:
https://ls1tech.com/forums/showthrea...ght=alternator
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91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
