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How to check alternator with volt meter?

Discussion in 'Off Topic Threads' started by blkcloud, Oct 27, 2010.

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  1. blkcloud

    blkcloud Active Member

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    My tractor is acting up, the John Deere guy said to check my alternator, I have a new digital volt meter but have no clue how to use it..lol.. what setting do I turn the dial to to check the out put? thanks!
     
  2. lostandout

    lostandout Member

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    set the dial to 12 v or it may have a vwit6h a double line over it should show dc on read out but the black lead to the alu part of the alternator and the red to the pos lead should read someware about 13 to 13.5 volts or you can pull the pos lead from your battery if the moter dies your alt is bad
     
  3. blade819

    blade819 Well-Known Member

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    Turn it to DC Voltage. With the engine off take a read on your battery, it should be around 12 volts. Now start the engine and do the same measurement across the battery, it should read about 13 volts or higher. If it does, that means your alternator is working charging your battery.

    blade819
     
  4. wireguy

    wireguy TS Member

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    You can't just check the alternator, you have to check the entire system, battery, alternator, voltage regulator. With only a volt meter you can't determine whether a problem is alternator or voltage regulator. You need to be able to measure large volume DC current to see if the alternator is producing current. You also need to be able to load the battery hard to get the alternator to produce current, it only produces on demand.
     
  5. likes-to-shoot

    likes-to-shoot Well-Known Member

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    Almost every auto parts store (at least here in the midwest) will check Alternators, Batteries and Starters for free.
     
  6. phirel

    phirel TS Member

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    likes-to-shoot- Sometimes it is not convenient to drive a tractor to an auto parts store.

    Pat Ireland
     
  7. Quack Shot

    Quack Shot Active Member

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    If you have no idea of how to use a meter, then it might pay to have someone who knows how to diagnose the systems do it for you. Voltage alone won't tell the whole story. You could have failed rectifiers and the voltmeter won't tell you that unless you know what you are doing. If you just want to check battery voltage and running voltage. Take a reading across the battery with the engine off. Start the engine, let it stabilize a bit and check the voltage across the battery again, this time holding the engine rpm up off of idle. This will give you a rough idea that the alternator is putting out "something" or not. You also need to check the condition of the battery and current output at full load, along with checking for any AC current, indicating failed rectifiers. Checking voltage drop under load, across the ground and charging circuits might be a help.

    You also need to explain just what "Acting Up" is. Fails to start? Battery goes dead?
     
  8. blkcloud

    blkcloud Active Member

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    Acting up means.. My tractor is a 6200 JD 4x4 cabbed tractor, diesel engine.. on flat ground it runs like a race horse, but.. when you start up the slightest incline the tractor shuts off.. the JD mechanic said it sounds like not enough power is getting to the fuel solenoid..?? I took the battery out of my truck and put in the tractor saturday while I was picking corn (after it had quit 20 times and ran the old battery down) the tractor ran fine for a few rounds then quit again.. thanks!
     
  9. Quack Shot

    Quack Shot Active Member

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    There are a whole mess of other things that could cause the same symptoms. Check the battery and alternator output voltage, but if it's going down that quick, I'd suspect something else. The part about the incline bothers me, since the fuel shutoff solenoid is usually open or closed. Maybe you have an issue in the fuel system. I've seen some suck air or plug filters to the point where they will just about run level. If you have electric glow plugs, I'd also make sure they are shutting off. It's usually controlled by a relay. They can drain a battery pretty quickly, depending on the type. All I can remember about the model is that I think it comes with a 4 cyl Turbodiesel of German manufacture. I don't remember too much about the fuel system, but seem to remember one of these set up as a backhoe/loader in the late 90's. There was an algae growth in the fuel tank that had this thing doing almost what you are describing. Ran OK until you put a little load on it. Flushed the fuel tank, lines, replaced filters, etc. It cleared up and ran fine after that.
     
  10. Catpower

    Catpower Molon Labe TS Supporters

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    Blk cloud, check the alternator the way the first couple of posts said to, it should be putting out 13-14.5 volts, if it isn't take it too an alternator shop, or open your wallet wide and take it to Mother Deere

    I think the 6000 series had an electric fuel pump right where the line comes out of the fuel tank, that could also be a problem

    There is also an inline check valve that they put right under the platform, that could be letting the fuel leak back, and there is also a small diaphram inside the hand or priming pump on top of the fuel filter

    I have a bunch of JD tractors, and we do most of the work on them, some of the mechanics they use are great and some not so great, I had problems with a 5625 MFWD that it would lose it's prime when you shut it off, sometimes every time sometimes once in a blue moon, drove me nuts, called the service damager at my local Deere shop, he said there was no check vavle, I said there had to be, so I spent a week or two with Eau De Diesel fuel getting poured on me, because everything was underneith and I had to drain the tank every time to do any work on the system, anyway I jacked with it and finally looked up on www.jdparts.com and saw in the parts catalog where the check valve was, and it has run perfectly since

    If it has enough power to start then it has enough power to run the fuel pump and solinoid, IMHO I think you have a fuel delivery problem, and the lower the fuel level in the tank the worse they can be

    Actually I think the fuel systems in the newer ones are a PITA
     
  11. blkcloud

    blkcloud Active Member

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    I just got in from putting the alt. back on, hooked up the jumper cables and after a few cranks it started.. but, before it started I noticed fuel coming out of the top of the fuel filter..which has about 15 minutes of running time on it.., I went around to loosen one of the injector lines and felt heat coming from the solenoid.. it was so hot you couldnt touch it.. I didnt loosen any lines but kept cranking on it and it did start.. I think it may be the solenoid.. I'll order a new one tomorrow.. I dont think they are supposed to get fire engine hot with just the key on.. thanks!
     
  12. ricks1

    ricks1 TS Member

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    you found your problem also if you dont know web site Tractor by Net great site
     
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