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#1 |
Senior Member
Join Date: Apr 2005
Location: Joppa, Maryland
Posts: 4,408
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High Voltage Problem
I just finished rewiring for an internal reg. alternator and am having voltage problems, I think. I rewired as described in the FAQ. I'm reading 17.5 volts at the battery at idle and 18.5 volts at higher RPM. I don't think this is right as this is overcharging the system. Isn't it only supposed to be around 14 volts.
This is a new reman alternator that I installed. Hope someone can let me know what's up, if this is normal or?
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1997 GMC Sierra Ext 1965 Mustang |
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#2 |
'65 GMC Project
Join Date: May 2005
Location: Abbotsford, BC
Posts: 653
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Yeah, somethings definetly screwy. Your right, the battery should read somewhere around 14 volts at idle. Either your new alternator's internal voltage regulator is defective or your wiring is incorrect.
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#3 |
Back in the sticks
Join Date: Jan 2001
Location: Fordland, MO
Posts: 3,188
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What was the condition of the battery before you started it back up? What are you reading the voltage with and where? Need those answers, but 18.5 while charging, if the battery is low might not be bad, as long as it drops down after its recharged. If you are reading that at the alternator output, check it somewhere else in the circuit to see if it is dropping down once its in the system. If you have a voltmeter, read the battery terminals with it shut off and then again with the truck running. Normally, you will see about 14.5 volts with it running and a normal charging situation gonig on(that is, battery not fully discharged.) Jeff
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1971 Cheyenne C-10 w/700R4 and Tuned Port Injection 1969 K5 Blazer w/Tuned Port 2010 2SS/RS Flaming Orange Camaro 2011 K1500 Suburban 2014 K1500 Pickup 2008 Nissan Altima? The wifes' hoopty |
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#4 |
Senior Member
Join Date: Apr 2005
Location: Joppa, Maryland
Posts: 4,408
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I was checking the voltage at the battery with my dig. volt meter and set for dc volts. The battery is getting old, (about 7 yrs) and I have had to charge it recently. I've just never had a volt spike like this before. I'll try and take a reading at the alternator and see what I get......Like I said, I just bought this alt from Advance Auto today.....
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1997 GMC Sierra Ext 1965 Mustang |
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#5 |
Registered User
Join Date: Feb 2002
Location: Vacaville, CA
Posts: 2,746
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You said the magic words, reman & Advance. Its probably a bad alt. either that or you didn't get an internally regulated alt.
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![]() ![]() 99 Pontiac S/C GTP, SLP Ram Air hood, GMPP Konis & springs 95 Neon ACR, MP PCM, AFX UDP, 3.0 CAI |
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#6 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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I have never heard of an alt putting out more VOLTS to charge up a low battery....they will however put out more [/i]AMPS[/i] to recharge a dead player though.
IO think neon larry hit the nail on the head there...either not an internally regulated alt...or it's a worthless one. |
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#7 |
blood type; Retumbo
Join Date: Jan 2004
Location: next to my reloading bench
Posts: 10,269
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I am leaning towards the "junk alt" side. I personally REFUSE to buy an alternator or starter from anyone. they are so easy to do yourself. I spent about $60 in parts to do my 100A junk yard jewel (get one from an 85ish Olds with heated rear window)
if you had that thing running with any stereo or other higher tech (non-antique) equipment you may have blown that as well
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Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card |
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#8 |
Registered User
Join Date: Jul 2005
Location: Mexico
Posts: 92
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The oposite
I am reading 12.4 at idle, new alt , new engine harness, external regulator, whats happening?
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#9 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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You aren't charging. Need to check out which component isn't working.
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#10 |
Senior Member
Join Date: Apr 2005
Location: Joppa, Maryland
Posts: 4,408
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I've rechecked the wiring conversion I did, and is correct according to the FAQ. I'm going to start the truck up again, and while it's running, disconnect the + bat. cable and see what that (maybe junk) alt. is putting out then. I got a feeling that the alt. is junk. I wanted to buy a cheap one ($29.99) just to see if this change would work. Gotta feeling that I will be taking it back, at least I'm hoping that's what's wrong with this, and not any wiring problems......thanks for all the help guys......
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1997 GMC Sierra Ext 1965 Mustang |
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#11 |
Registered User
Join Date: Jul 2004
Location: Southern Tip of OHIO 45680
Posts: 49
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Put a new high amp alt in my ride...replacing an old one. It required a high amp wire kit (came with my painless harness) to reduce the load. Gives me one hot wire to the fuse block like normal and another off to a Maxi-fuse off the battery/starter.
Before I did this, I fried some wire and the Flex-o-lite control on my fans...thank goodness for warranty (they were real cool about my stupidity). My voltage was through the roof too.
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Only the Mediocre are always at their best... '69 GMC LWB 406, TH400, 3.73 Posi' Things I've learned from my truck...If I was an automaker, my vehicles would be overpriced, run rough, and get 5MPG. |
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#12 |
Senior Member
Join Date: Apr 2005
Location: Joppa, Maryland
Posts: 4,408
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I took the reman alt back to Advance Auto to check. This alt was putting out so much voltage, that it cooked one of their connections. That was funny. I told them to give me my money back. Didn't want another one from them. I then went across the street to Auto Zone and bought one of their Duralast with lifetime warranty for $10.00 more. Put it on the truck. Charging at 14.1 volts. I should have done that in the first place. I just hope I didn't cook any of my electrical things, like maybe the HEI mod. I'll wait and see......Never again, Advance!!!!
Thanks for all the help guys.............
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1997 GMC Sierra Ext 1965 Mustang |
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#13 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Normally that is the other way around. Auto Zone has junk alt.
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