Testing Alternator on voltmeter!!
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Testing Alternator on voltmeter!! - 3/9/2008 5:57:39 PM
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lionel2
Posts: 97
Joined: 12/10/2006
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Does testing the alternator with a voltmeter tell if the alternator is still good?? if my alternator puts out 14.4V does this mean it is normal and just fine?? if it is below 12V then i might need to replace the alternator. Because I am running alot of aftermarket electronics, such as radar detector, 2 amplifiers, subwoofers, and ipod hooked up to head unit. It draws alot of current on my stock 105A alternator and I have a feeling my alternator has had it. So i will test it tomorrow with the volt meter and see what it puts out. I have 2 gauge wiring all thorughout for the 2 amplifiers. should I upgrade to a 140A alternator?? thanks.
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RE: Testing Alternator on voltmeter!! - 3/10/2008 3:46:12 AM
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thegr81
Posts: 2639
Joined: 1/16/2007
From: PHOENIX,AZ
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See what it puts out with the vehicle on and everything running at the same time. If it drops significantly then I would upgrade to a better alternator and battery!! By the way what battery are you running?? I have a optima yellow top in mine and I am running to air compressors off my factory alternator and optima battery and they both draw as much as what your using in yours!!
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2001 2wd 4.3 vortec v6
"I'm not fat, I'm a minitrucker"
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RE: Testing Alternator on voltmeter!! - 3/10/2008 5:09:40 AM
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lionel2
Posts: 97
Joined: 12/10/2006
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Well, I have a volt meter built into my head unit, when I slam the system it says at about 14.1 to 14.2 volts. All in all it stays above 14 volts. I am only running about 600w rms. 500w to subs and 100w to doors and dash. I have a prostart battery I believe. its rated at 815CC. Last year i had the battery tested and it put out 691CC. Would you say the battery needs replaced if it is this low?? Yes, I am going to get a yellow top for my next battery. What group size do you use on the blazer?? my battery thats in there now is a group 75/25. Use the same size?? I want it to fit like the original. But, if i replace the battery, will my alternator die because of the new battery needing so much juice it drains the alternator?? thanks.
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RE: Testing Alternator on voltmeter!! - 3/10/2008 5:31:28 AM
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thegr81
Posts: 2639
Joined: 1/16/2007
From: PHOENIX,AZ
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No a new battery wont drain your alternator!! The yellow top that I have in mine and it fits in the stock location with the factory battery hold down is
Model #: 3478DT
part #: 34/78-0Y
I got mine from autozone for 280.00 bucks if I remember right!! I have had it for 1yr and 4months zero problems. Your battery might be a servicing type were you have to pop the caps on top of it to check water level, if that level is low then its not retaining the charge from the alternator therefore effecting the charging system greatly!! The optima batteries are cell type batteries and do not require servicing as far as popping any caps off to check the fluid level in them!! I used a red top in my old 99 nissan maxima for 4yrs while I owned it and ran a air compressor for air ride and also had 3 10" subwoofers with two amps and they both were 1000bd fosgate amps and I didn't have any dimming of lights or lack of power from my charging system at all!!
_____________________________
2001 2wd 4.3 vortec v6
"I'm not fat, I'm a minitrucker"
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RE: Testing Alternator on voltmeter!! - 3/10/2008 6:56:41 AM
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lionel2
Posts: 97
Joined: 12/10/2006
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Yeah, If my battery that is in there right is bad, then I will get that yellow top, the 34/78 group size. My battery in my car right now is the liquid filled type. Well, I am running 3 12's in my blazer and my sub amp is running at 4 ohms at 500w rms and my 4 channel is 100w rms to my doors and dash, and i have a 100A fuse under the hood. 60A for sub amp and 40A fuse for 4 channel, But my 4 channel is a US Amps one and i know it draws alot, but its only a little one, the USA-425 2 ohm stable version 25x4 rms. I am going to get my alt and battery tested right now. I will let you know the results. thanks.
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RE: Testing Alternator on voltmeter!! - 3/10/2008 8:59:10 AM
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lionel2
Posts: 97
Joined: 12/10/2006
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Ok, just got home from battery shop. They tested my battery and it is rated at 650CCA and it is putting out 600CCA, and the man said the battery is just fine, but when it drops below 500CCA, i need to replace it. Then, here is the bad news, the alternator was tested. I turned on the car and he tested the alternator and it was reading .8 to .6!! Not sure what this is measured in, but he said the alternator is pretty much dead and my car was just running off the battery power. Because i had my battery tested in june 2007 and it was 700CCA and now in march 2008 its 600CCA, so its dropping rapidly. the battery will be dead soon. So looks like I have to replace the alternator with a new one, maybe a bigger one, like 140A. And then I think my alternator should juice up the battery pretty good. Will i need to replace my battery if i got a new alternator?? even if my battery is still at 600CCA?? How much is a new alternator?? and how much is a bigger new alternator, like a 140A one?? thanks.
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RE: Testing Alternator on voltmeter!! - 3/12/2008 5:06:02 AM
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lionel2
Posts: 97
Joined: 12/10/2006
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Does the 2000 blazer have a 100A or 105A alternator?? because my alternator says delphi on it, its original equipment that came with the car, but cannot find out how big the alternator is, a 100 or 105A alternator. thanks.
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RE: Testing Alternator on voltmeter!! - 3/12/2008 6:27:52 AM
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swartlkk
Posts: 15304
Joined: 5/1/2005
From: Waterloo, NY
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105A & Delphi was the OE supplier. Can we keep the discussion on the alternator in this thread and not your Yellow Top thread?
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Kyle-
My Restoration Projects
Please Do Not PM for Tech Help
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RE: Testing Alternator on voltmeter!! - 3/12/2008 7:31:05 AM
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lionel2
Posts: 97
Joined: 12/10/2006
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No problem, So will a 105A alternator be good enough to run all my electronics in my blazer. As far as electronics, I have a radar dectector, sound system that is 600w rms total with 2 amps and a 100A fuse under hood and last, I have the little Ipod computer under my dash to run my ipod when it is hooked up to my car. Because, I got all this stuff back in 2005 and never had a problem with the alternator until now, does that mean in 3 or 4 years from now with the new alternator installed that I might have to get another new alteranator?? Or am I good for another 90,000 miles with a brand new alternator?? I guess its just old age for the alternator and all those electronics I hooked up. thanks.
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RE: Testing Alternator on voltmeter!! - 3/12/2008 8:56:55 AM
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swartlkk
Posts: 15304
Joined: 5/1/2005
From: Waterloo, NY
Status: online
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Ah, I knew there was another thread by you discussing this.
If you are already having to change it out, I would go with a larger unit. Not a rediculously expensive one, but something that puts out more won't hurt.
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Kyle-
My Restoration Projects
Please Do Not PM for Tech Help
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RE: Testing Alternator on voltmeter!! - 3/12/2008 10:46:34 AM
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lionel2
Posts: 97
Joined: 12/10/2006
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Ok, will do, I asked my mechanic that I would like a bigger alternator. Guess they will try and get one, if not, guess i will have to go with the 105A alternator. But, if i do get the 105A alternator will it be okay to use with all these electronics i have hooked up?? or will it be dead in 3 or 4 years? thanks.
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RE: Testing Alternator on voltmeter!! - 3/13/2008 11:09:38 AM
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lionel2
Posts: 97
Joined: 12/10/2006
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Ok, I took my car to the shop early, as it turns out, I do not need a new alternator. My mechanic put the multimeter on my battery and set it to volts and it read 14.2 Volts, Which is normal and very good. Turns out the man at the battery place was wrong and cost me time and all this. So I went back to battery man and told him that he did it wrong. Big boss came out and yelled at the boy in front of me. Did not expect that, but then again he cost me time and the hassle and embarassment when i told my mechanic all this. Bottom line is my battery and alternator are fine for a while. Thanks for all the help in the matter.
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