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hitmen45venom
New User
Mar 27, 2007, 8:39 PM
Post #1 of 8
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AC VOLTAGE TO BATTERY
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HOW MUCH AC VOLTAGE TO THE BATTERY IS EXCESSIVE IM GETTING .053. I THINKING THE ALTERNATOR HAS A BAD DIODE.
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joblake
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Mar 27, 2007, 10:20 PM
Post #2 of 8
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Re: AC VOLTAGE TO BATTERY
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How much DC voltage do you have?
What are you using to read the AC voltage?
Are you right across the battery terminals?
.052v is nothing to worry about.
Why do you think you've got a bad diode?
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hitmen45venom
New User
Mar 28, 2007, 10:24 AM
Post #3 of 8
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Re: AC VOLTAGE TO BATTERY
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12.6 car off
13.54 car on, with blower motor on, and radio
A FLUKE 73 MULTIMETER
going right across battery terminal
I think its a bad diode because I have ac voltage to the battery
I was told a certain amount was too much
THANKS FOR THE HELP
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joblake
User
Mar 28, 2007, 1:06 PM
Post #4 of 8
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Re: AC VOLTAGE TO BATTERY
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Like I said, .053 vac is nothing.
I'm curious what you get for AC voltage with the car off...if you still get something then you're just picking up power line noise from the air.
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hitmen45venom
New User
Mar 28, 2007, 1:23 PM
Post #5 of 8
(5875 views)
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Re: AC VOLTAGE TO BATTERY
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car off zero ac volts
car on .053 ac volts
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joblake
User
Mar 28, 2007, 2:34 PM
Post #6 of 8
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Re: AC VOLTAGE TO BATTERY
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OK. That proves that what you're seeing is really coming from the alternator.
Just for the heck of it I just measured my truck's "ripple", i.e. AC voltage and it was around .035vac.
I'd say your .05 is just fine.
To put it into perspective, if your DC voltage is 14V, then you have less than one half of one percent of ripple.
That's virtually nothing.
Do you have a battery charging system problem that led you down this path?
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hitmen45venom
New User
Mar 28, 2007, 5:04 PM
Post #7 of 8
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Re: AC VOLTAGE TO BATTERY
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Battery was discharged one night after driving, had to jump it.
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joblake
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Mar 28, 2007, 5:35 PM
Post #8 of 8
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Re: AC VOLTAGE TO BATTERY
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I'm just going to through a bunch of stuff so bear with me...
When the car is running you should have somewhere around 14+ volts across the battery. With 13.54v you're a little low but I don't know if it's necessarily a problem.
How old is your battery? Maybe it can't hold a charge?
Also if the alternator belt is glazed it could be slipping when under a heavy load at night with headlights, heater, etc. on.
And how good and clean and tight are your connectors on your battery terminals?
Did the battery not start the car RIGHT after your drive or was it the next morning
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