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Troubleshooting Electrical Draw: volt meter 101

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    #1

    Troubleshooting Electrical Draw: volt meter 101

    Hey guys, so I recently got another e30 and need help tracking down a draw. I have a volt meter, but am not much of an electrical guru. I am curious what setting I should set the meter to and what to look for when going down the slots in fuse box.

    Also, it looks like fuse 20 burned - I will be throwing in a spare fuse box soon (I am following the assumption that 89 325i box is the same as a 91 318i). Let me know if I need to clarify anything. Thanks.










    Last edited by ethirtydavid; 03-02-2009, 07:02 PM.
    Tags: None
    #2
    How do you install a voltmeter in a car? - Answers
    http://wiki.answers.com/Q/How_do_you_test_for_current_draw_in_a_car_using_a_volt_meter
    You get a properly sized low value resistance of high accuracy like 1% known resistance say 1 ohm. Then you place the wire that you want to measure in series with the resistor and place the voltmeter across the resistor. So if you have a 1 ohm resistor and the meter is reading 1 volt then you have 1 amp flowing in there. you need to unhook the negative battery cable and set your mutimeter to amps and connect it between the negetive cable and the battery and that will tell you what kind of draw you have just make sure that your multi meter is set up right You can't measure the current drawn by a car. The current is WAY to high for most meters. Most meters will only measure up to 10Amps. The first guy has the best idea. Get a 1ohm resistor and measure the voltage across it. The voltage measured divided by the resistor value equals the current consumption. If you have to use a voltmeter the first answer is right just make sure its a 5 or 10 watt resistor at least and don't turn the key definitely.Just measure for current being taken that shouldn't be. And yes you can use an ammeter to measure the current make sure its on the correct range (1 amp or 10 amp is better) and don't turn the key just check for current being drawn other than the starter and relay.If you turn the key big trouble lol.Probably burn out the meter burn yourself if using a resistor or just not good :) And don't wory about a 1% resistor 5% or 10 % is fine to just get a good idea of the amount of current.


    Unload those tires asap.
    '96 328is
    '97 m3
    '04 zhp

    Comment

      #3
      Originally posted by Mless5 View Post
      http://wiki.answers.com/Q/How_do_you...g_a_volt_meter

      Unload those tires asap.
      I had a hard time understanding the answers in your link.
      I saw this diagram,
      but unsure what to make of the results. I have my ohm meter set on DCV 20 and it reads out jumping around between 12.40 and 12.60..

      I know there is a draw, what I am really interested is testing each slot in the fuse box.

      To be more direct, what setting do I set my ohm meter on; what should I be looking for on the read-out?
      Thanks guys

      Comment

        #4
        You want to measure amperage, not voltage. The dcmA in the picture you posted stands for DC Milliamps. 1000mA is 1 amp. Hook the meter inline with the battery like the picture above with it set to amps. Then, start pulling fuses. When the reading drops, you know what circuit has a draw based on the fuse you just pulled. Don't forget to turn off/pull the bulb out of the trunk light or that will throw off the test.

        Comment

          #5
          Ill give this a shot

          Comment

            #6
            When I set it to dca 20m and connect it as shown in picture above ^ all I get it 0.0 read-out.
            If I have something set wrong, let me know :)

            Comment

              #7
              figured out my problem - multi-meters shot - makes sense now..
              I'll get back to this in a day or so

              Comment

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