 No Alt. light after start up but battery not topping off .. |
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| Literati914 |
 Aug 9 2025, 10:35 AM
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Advanced Member  Group: Members Posts: 2,086 Joined: 16-November 06 From: Dallas, TX Member No.: 7,222 Region Association: Southwest Region  |
My battery was bought last month.. Alternator light comes on with the key on, but goes out at start up. Battery keeps running low and eventually won't start the car. Does this point to anything usual - VR maybe?
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Replies
| VaccaRabite |
Aug 28 2025, 10:02 AM
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En Garde! Group: Admin Posts: 13,779 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region 
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It does not take much of a voltage drop to discharge your battery.
I had about a 1.5v drop between the alternator and the battery due to the ground path going through a powdercoated doghouse. They had taped off the bolt holes, but there was still enough resistance to cause an issue. I ran a stout wire from the body of the alternator to the ground lug on the driver side of the chassis where the relay board grounds. Problem solved. When I changed engines I kept the extra ground - easy enough to do though I admit its a belt and suspenders option while everyhting is working. Point being, if the you have paint or corrosion around your doghouse (which is the ground path for your alternator) then you are going to have that voltage drop. It takes 10 minutes to add a ground to the alternator housing up though the tin to the ground lug behind the relay board. Good luck! Zach |
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Posts in this topic
Literati914 No Alt. light after start up but battery not topping off .. Aug 9 2025, 10:35 AM
GregAmy Does this point to anything usual - VR maybe?
What... Aug 9 2025, 10:44 AM fixer34 Could be several things but VR is a likely suspect... Aug 9 2025, 11:24 AM TheCabinetmaker Check the belt tension Aug 9 2025, 12:04 PM Literati914
Does this point to anything usual - VR maybe?
Wha... Aug 10 2025, 07:14 PM
GregAmy
update - the bulb is not blown. I can get it to l... Aug 10 2025, 08:13 PM
Lockwodo
[quote name='GregAmy' post='3218602' date='Aug 9 ... Aug 10 2025, 09:41 PM dtmehall I experienced similar symptoms about 4 years ago.
... Aug 10 2025, 07:24 PM Spoke There is a quick test you can do on the alternator... Aug 10 2025, 07:26 PM Literati914 just noticed that my alt bulb has blown after tigh... Aug 10 2025, 07:26 PM Literati914 update - the bulb is not blown. I can get it to li... Aug 10 2025, 07:42 PM Literati914 Alt light with ground provided by test light… li... Aug 10 2025, 07:54 PM Literati914 You can see the rat’s nest of wires here Aug 10 2025, 07:55 PM Literati914
update - the bulb is not blown. I can get it to ... Aug 10 2025, 08:39 PM Literati914
[quote name='Literati914' post='3218779' date='A... Aug 10 2025, 09:17 PM Spoke
removing the alt plug at the relay board in order... Aug 11 2025, 05:30 AM Literati914
If the battery voltage, measured at the terminals... Aug 11 2025, 01:35 PM Lockwodo
If the battery voltage, measured at the terminal... Aug 12 2025, 12:04 PM Literati914
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If you unplugged the alternator please plug it... Aug 11 2025, 02:32 PM Spoke
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If you unplugged the alternator please plug i... Aug 11 2025, 04:02 PM Literati914
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What is the battery voltage at idle? Positive ... Aug 11 2025, 04:27 PM Spoke
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What is the battery voltage at idle? Positive... Aug 11 2025, 06:41 PM Literati914 I did the test - jumper wire between D+/DF (with V... Aug 11 2025, 07:06 PM Literati914
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Can you measure the battery voltage and D+ wi... Aug 11 2025, 07:15 PM Spoke
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Can you measure the battery voltage and D+ w... Aug 11 2025, 11:34 PM GregAmy I tend to agree that it's a diode, which is a ... Aug 12 2025, 07:50 AM Superhawk996 I’ve been reluctant to chime in . . . . Cause Iâ... Aug 12 2025, 09:14 AM GregAmy ^^^ Good points. Aug 12 2025, 09:58 AM Literati914 Still dealing with the problem of alternator not c... Aug 27 2025, 04:17 PM emerygt350 I have really enjoyed my negative terminal to the ... Aug 27 2025, 04:59 PM Literati914 I've already installed something similar - top... Aug 27 2025, 05:18 PM Literati914 Also, I just found the following break in the wire... Aug 27 2025, 06:36 PM Superhawk996
Also, I just found the following break in the wir... Aug 28 2025, 11:38 AM emerygt350 Might be, however I wouldn't rely on the 50 ye... Aug 27 2025, 07:50 PM Literati914 OK then, the plan is to run a wire off the lower p... Aug 28 2025, 10:24 AM KELTY360 Beware adding two fixes at once. The added ground ... Aug 28 2025, 11:02 AM Literati914
If you want to measure the voltage drop in that c... Aug 29 2025, 11:50 AM Superhawk996
Probably normal :confused: but would that be an... Aug 29 2025, 07:30 PM Literati914
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If there is any doubt in your mind about paras... Aug 29 2025, 08:50 PM |
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