Need Alternator GURU---Help
Instructor
Joined: Jun 2011
Posts: 216
Likes: 0
From: Brunswick Georgia
I have never looked at a service manual for alt dia. it is something I learned yrs ago. I understand the reasoning for that but for the most part it is hug wash. When they bench test a alt they test it just like I said but off the car. Your not running it forever just a sec or to to see if the alt can put out and to elimiate other things. If anyone does not like my susgetion I have no problem I understand. I do know at least 3 people in the last moth have used my way on her without ant ill effects and it help them dianoise their car
Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
i nget what you are saying and maybe I should explain better but in reality charging systems are pretty simple. He said he had 12 volts on the smaller terms and 12 volts on the large term that is all you need to charge. infact you really only need 12 volts on the f term for it to charge the f term excits the windings so the alt can charge.
Thread Starter
Racer
Joined: Sep 2007
Posts: 493
Likes: 0
From: Eden Utah
i nget what you are saying and maybe I should explain better but in reality charging systems are pretty simple. He said he had 12 volts on the smaller terms and 12 volts on the large term that is all you need to charge. infact you really only need 12 volts on the f term for it to charge the f term excits the windings so the alt can charge.
Instructor
Joined: Jun 2011
Posts: 216
Likes: 0
From: Brunswick Georgia
I am not sure you ever did my battery and short check. I will try again.
With the engine OFF:
1) How are you charging your battery now?
2) What voltage do you have when your battery is charged? 12.0 12.3 12.5 12.7 ?
If you answer those 2 questions we can continue.
.
.
With the engine OFF:
1) How are you charging your battery now?
2) What voltage do you have when your battery is charged? 12.0 12.3 12.5 12.7 ?
If you answer those 2 questions we can continue.
.
.
Team Owner
Joined: Sep 2003
Posts: 25,373
Likes: 2,734
I don't have an '85 FSM but I believe with an old 17SI alternator if you unplug the connector the voltage for terminal 1 should be maybe 2 - 4 volts supplied from the ignition through a resistance wire in the circuit. I would think a 10 Ohm resistance accomplishes that. Terminal 1 I believe should be brown. You keep mentioning 12V everywhere and I believe it's maybe important that you further define just what you have if you're looking for help. If the connector is good, the two fusible links from the starter solenoid are good and you have 2 - 4 volts at terminal 1 I'd think it should be charging.
You can't honestly evaluate it without the knowledge of the battery condition and I'm guessing from your remarks I'd likely go buy one. You've not once mentioned that you've checked things that need checked before putting a "load" on any electrical charging or cranking device.
The battery terminal needs to be at 12V to do the checks for terminal 1 and you don't seem to have that. The key I believe should only need to be in the run position. I don't believe it needs to be running.
You can't honestly evaluate it without the knowledge of the battery condition and I'm guessing from your remarks I'd likely go buy one. You've not once mentioned that you've checked things that need checked before putting a "load" on any electrical charging or cranking device.
The battery terminal needs to be at 12V to do the checks for terminal 1 and you don't seem to have that. The key I believe should only need to be in the run position. I don't believe it needs to be running.
Last edited by WVZR-1; Jun 12, 2014 at 09:03 AM.
Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
Wayne I just walked back in the door. I am speculating that your battery is shorted. By starting the car then removing the post term off the battery you are taking the battery out of the loop and you will get a true indication if your alt is putting out. All you need for that thing to put out is 12 vlots on the f term and 12 volts on the large term you have voltage there and it does not charge then it is a bad alt.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
How can the battery be shorted and still start the car?
^This^ (in bold) is the "red flag", for me. you have BAT volts when not running...but
no volts...when running"? That is not right. You should have BATv there always...even if it's not charging. I'd be checking the integrity of that wire.
With key off, I have 12 Volts to the large red wire that bolts to back of alternator, and I have 12 volts to the red wire in the plug. No volts to the white wire in the plug. With key on I have 12 volts to the white wire in the plug.
no volts to large red wire when running, both wires in the plug are 12 v
no volts to large red wire when running, both wires in the plug are 12 v
no volts...when running"? That is not right. You should have BATv there always...even if it's not charging. I'd be checking the integrity of that wire.
Last edited by Tom400CFI; Jun 12, 2014 at 03:28 PM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Thread Starter
Racer
Joined: Sep 2007
Posts: 493
Likes: 0
From: Eden Utah
How can the battery be shorted and still start the car?
^This^ (in bold) is the "red flag", for me. you have BAT volts when not running...but
no volts...when running"? That is not right. You should have BATv there always...even if it's not charging. I'd be checking the integrity of that wire.
^This^ (in bold) is the "red flag", for me. you have BAT volts when not running...but
no volts...when running"? That is not right. You should have BATv there always...even if it's not charging. I'd be checking the integrity of that wire.
Thank you, thank you....The Guru finally showed up. Tom gave me one simple test...Run a wire from the main post on the altenator, to the positive on the battery. BAM!! 13.8 volts. It looks as though I have a fusible link that is out...
Again Tom, thanks..
Instructor
Joined: Jun 2011
Posts: 216
Likes: 0
From: Brunswick Georgia
I think this was addressed in post 3 and 4. If this is the culprit, let us know. Did you need a new alternator or was it just the fusible link?
Team Owner
Joined: Sep 2003
Posts: 25,373
Likes: 2,734
OP - All you've confirmed is that the alternator you were sold is doing as it's supposed to do. It passed the test on the bench, you can't expect it to do the same on the car unless the charging system is A1. You've not evaluated "squat" - you've no idea what took out your original if it was indeed bad. You've only confirmed that the new is functional.
You've got much more to do! First to do is a "load test" of at least the battery but I'd consider a load test of the entire system "on the car"! A "load test" on the car could evaluate the output of the alternator in AMP at idle, at speed and also you could confirm the starter condition in the same test. A replacement alternator may not last long when put into service in an electrical system that is less than A1.
You've got much more to do! First to do is a "load test" of at least the battery but I'd consider a load test of the entire system "on the car"! A "load test" on the car could evaluate the output of the alternator in AMP at idle, at speed and also you could confirm the starter condition in the same test. A replacement alternator may not last long when put into service in an electrical system that is less than A1.
Last edited by WVZR-1; Jun 12, 2014 at 05:25 PM.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
His original wasn't bad. Not likely, anyway.
The stumbling block here, was that he got 12.Xv on the "BATT Term" post on the alt. (not running). The led him to believe that the B+ wire had continuity. The "no volts...when running", on the same wire was the clue (at least to me anyway).
Wayne ran a jumper wire from B+ to "BATT Terminal" on the alt, to test the BATT wire by bypassing it. As he said,
"Run a wire from the main post on the altenator, to the positive on the battery. BAM!! 13.8 volts."
So it appears that the BAT wire is losing continuity, under a load; wire, connections or fusible link is toast...it would seem.
The stumbling block here, was that he got 12.Xv on the "BATT Term" post on the alt. (not running). The led him to believe that the B+ wire had continuity. The "no volts...when running", on the same wire was the clue (at least to me anyway).
Wayne ran a jumper wire from B+ to "BATT Terminal" on the alt, to test the BATT wire by bypassing it. As he said,
"Run a wire from the main post on the altenator, to the positive on the battery. BAM!! 13.8 volts."
So it appears that the BAT wire is losing continuity, under a load; wire, connections or fusible link is toast...it would seem.
Team Owner
Joined: Sep 2003
Posts: 25,373
Likes: 2,734
His original wasn't bad. Not likely, anyway.
The stumbling block here, was that he got 12.Xv on the "BATT Term" post on the alt. (not running). The led him to believe that the B+ wire had continuity. The "no volts...when running", on the same wire was the clue (at least to me anyway).
Wayne ran a jumper wire from B+ to "BATT Terminal" on the alt, to test the BATT wire by bypassing it. As he said,
"Run a wire from the main post on the altenator, to the positive on the battery. BAM!! 13.8 volts."
So it appears that the BAT wire is losing continuity, under a load; wire, connections or fusible link is toast...it would seem.
The stumbling block here, was that he got 12.Xv on the "BATT Term" post on the alt. (not running). The led him to believe that the B+ wire had continuity. The "no volts...when running", on the same wire was the clue (at least to me anyway).
Wayne ran a jumper wire from B+ to "BATT Terminal" on the alt, to test the BATT wire by bypassing it. As he said,
"Run a wire from the main post on the altenator, to the positive on the battery. BAM!! 13.8 volts."
So it appears that the BAT wire is losing continuity, under a load; wire, connections or fusible link is toast...it would seem.
Thread Starter
Racer
Joined: Sep 2007
Posts: 493
Likes: 0
From: Eden Utah
The old alternator was bad.. It showed bad on the tester. When I put the new one on, I got no charging. I crawled under the car yesterday and had a look, they looked fine. I will get the car up on a rack and pull the starter so I have room to see and fix the links. The problem yesterday was I was getting continuity through the fusible links, and that is what threw me. Tom suggested that one of the links might be frayed enough to show 12 v on the multi-meter, but not have enough wire left to really pull enough amps.
Team Owner
Joined: Sep 2003
Posts: 25,373
Likes: 2,734
It's a shame you didn't have a little more warning of the failure. It would certainly have been the opportunity/excuse to do an upgrade to the CS alternator which is considered much more reliable and efficient while you were working.
Thread Starter
Racer
Joined: Sep 2007
Posts: 493
Likes: 0
From: Eden Utah
The alternator was a lifetime POS from Orieley...I do not have much faith in the product...Tell me about the CS and can I get it in a 120 amp
Last edited by T. Wayne Nelson; Jun 12, 2014 at 07:17 PM.
Team Owner
Joined: Sep 2003
Posts: 25,373
Likes: 2,734
http://forums.corvetteforum.com/c4-t...n-an-85-a.html
Hib Halveson did a piece many years ago and I'm not real sure of some of the part #'s he mentions but I could likely confirm. Here's a link to his comments. You'll have to go towards the bottom where it's mentioned SI to CS.
http://www.corvetteactioncenter.com/...red_parts.html
I would rely on the information from the CF post and there's many other threads I'm sure that mention the swap. I'd study it well before attempting. It should require little aggravation I'd think.
Good luck!
Team Owner
Joined: Sep 2003
Posts: 25,373
Likes: 2,734
Halverson mentions 321- 368 for a 120 AMP, I see a '92 - '93 is 124 AMP 321-552 and a '93 - '96 140 AMP is a 321-1112. I'd maybe see which your local has and compare the clocking and remember you might need to swap pulley. Do you still have your old core? I like the idea of a used if it were an original and not someone's reman. Notice on the CF thread the mention of a rear brace. The connector swap and you would be in business I think. Study and let us know!!