alternator high voltage

89supracrazy

New Member
Oct 31, 2009
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My car is putting around 17.2 volts at 3k rpms and 13.6 volts at idle. I have something also draining my battery. My battery is good because I have to take my neg. battery terminal off every time I park my car. Is this the culprit.
 

IJ.

Grumpy Old Man
Mar 30, 2005
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I come from a land down under
jetjock;1497626 said:
Trouble trouble, boil and bubble, boom if you're unlucky...

cauldron.jpg
 

CajunKenny

PULL MY FINGER. PLEASE!
Nov 15, 2007
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Sounds like regulation is gone. Like IJ and JJ said your battery will not survive.

If you're not electrically savvy, take it somewhere you trust and have it repaired. Electrical draws can be maddening to track down.

EDIT: I start to post and walk away for a DEW and come back and JJ snuck one in there... :)
 

supra_669

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Mar 24, 2008
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had the same problem with my supra ..... the diode in the voltage regulator has gone bad best bet is to replace the alternator. it will also cause ur battery to drain when the vehicle is shut off so if u dont plan to replace it soon disconnect ur battery when u park ur car so u dont have to replace that aswell
 

jetjock

creepy-ass cracka
Jul 11, 2005
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Redacted per Title 18 USC Section 798
I should point out due to the design of the regulator used an open in the external sense line will result in the same symptom: alternator output is automatically limited to between 13 and 17 volts. He should check that before replacing the alternator...
 

supra8795

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Feb 26, 2006
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I know this is an old thread but what did you end up doing to solve the problem? Was your battery hot if you touched it after having the car running for a bit? Im having a problem with my alternator and I took if off to get tested but it tested out just fine. Should i get it tested while the alternator is on the car to see if there could be something else wrong?
 

Nick M

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Sep 9, 2005
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supra8795;1547788 said:
I know this is an old thread but what did you end up doing to solve the problem? Was your battery hot if you touched it after having the car running for a bit? Im having a problem with my alternator and I took if off to get tested but it tested out just fine. Should i get it tested while the alternator is on the car to see if there could be something else wrong?

What is your symptom?
 

supraguy@aol

Well-Known Member
Dec 30, 2005
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Sounds like your battery might just be getting hot from continuous discharge, since you don't mention an overvoltage issue.
Something shorted?
 

Nick M

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supra8795;1548026 said:
Battery running hot, losing charge over night.

When a battery puts out electricity, the lead merges with the sulfuric acid to become lead sulfate. If it hardens if often will not reverse itself when charged. The only charge you have is a static charge, and that isn't much. It isn't that it can't hold its charge, it is that it never had one. If you have this condition, the water left in the battery will boil quickly.

Do you have a small charger? You can put the charger on the battery and see how high the voltage goes. It should only take a minute. If it goes above about 15.5 volts to charge, the battery is no good. The high voltage is a response to the high resistance.