Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

How to test for voltage leaks?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by TX Mudder, Jan 7, 2002.

  1. TX Mudder

    TX Mudder 1/2 ton status

    Joined:
    Jul 10, 2000
    Posts:
    2,514
    Likes Received:
    0
    Location:
    Houston
    Does anyone know how to test for voltage leaks? What I mean is, when the ignition is turned off, there should be only a minimal draw from the battery for, say, the clock and radio presets. If the wiring has shorts or other problems, it could draw more battery power and thus lead to a dead or weak battery. I want to check for this.
    I thought the idea was to take a multimeter and put the bl;ack on the battery negative and the positive on the block/frame/somewhere and see if there is any current detected. I keep getting zero when I do that and I'm wondering if I'm doing it right.
    I don';t have a radio or anything that SHOULD draw power while off (that I know of.)
    -- Mike

    <font color=blue> Married to a woman who understands the need for <font color=orange>Hugger Orange. [​IMG] <font color=blue>
     
  2. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Your method is mearsuring the voltage between ground and ground. [​IMG] That will only tell you if you have a poor ground between the battery and frame. What you want to do is check for current draw. To do this, the meter is set to measure Amps, then placed inline with one of the battery cables. Do NOT attempt to turn on any high-current devices (headlights, etc.) while the meter is in the circuit. Most can only handle 10 amps or so, then an internal fuse will blow.

    A few hundred milliamps of current with the key off and the doors closed (so the interior lights are off) is about all that it should read. 300-500 milliamps is all that I would expect on a vehicle with EFI and a digital radio. If it's higher than that, then start unplugging fuses from the fuse block, one at a time, while watching the meter. When the current draw drops, you've found the circuit that is drawing the extra current. Now you just have to determine what the problem is on that circuit. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  3. prjt_blzr

    prjt_blzr 1/2 ton status

    Joined:
    Mar 4, 2001
    Posts:
    352
    Likes Received:
    0
    Location:
    COS, CO
    Don't forget to disconnect the altenator as it can also suck the battery dry. Just did this a few week ago. Disconnected every fuse one at a time and still had a current draw. Scratched my head and disconnected the alt and walla. The diodes were toast.
     
  4. Chris Demartini

    Chris Demartini 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    2,406
    Likes Received:
    1
    Location:
    Dumont NJ 07628
    <font color=blue>What your describing is how you would check for excesive resistance in the ground circuit (you would have to set it on OHM's to do this), like others said, connect the DVOM in series with the negative cable and the negative terminal and set it on Amps. Then pull fuses until the amperage drops. Start with the cigerette lighter circuit. I belive the memory for the radio is in series with this circuit, so the wire that used to go to your radio could be grounding out.
     

Share This Page