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How to test for electric draw with keys off? (Dead battery in mornings)

Discussion in 'The Garage' started by TX Mudder, Oct 3, 2002.

  1. TX Mudder

    TX Mudder 1/2 ton status

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    I used to have an electrical book that explained this, but I can't find it.
    How do I test to see how much electricity is being used by my truck the the keys OFF, nothing on, parked.
    I keep having a dead battery in the morning.
    Just replaced the alternator with a 100 amp and also put in a new bigger battery a few minutes ago.
    Maybe my battery was just dying, or maybe I'm drawing too much juice...a short or something.

    Help is appreciated.
    -- Mike
     
  2. Disconnect the positive lead and hook and ammeter between the positive lead and the positive terminal on the battery.
     
  3. Skigirl

    Skigirl 1/2 ton status

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    Can also do it with negative lead and negative terminal. Shouldn't have more than 20 milliamp drain. There are quite a few posts on battery drains (many were mine /forums/images/graemlins/1zhelp.gif). Do a search, the whole procedure is written up there somewhere.
     
  4. Tweetysuarus

    Tweetysuarus 1/2 ton status

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    Ditto on disconect one post or the other and use Amp Meter in line! Most dead batteries i've run into are related to someone miss wiring the choke to constant hot source! If the choke is on all nite it will kill a good battery quick enough same with stereos & Amps. Needs to be on Ignition source. Hope this helps you try to locate the draw?
    Bill
     
  5. TX Mudder

    TX Mudder 1/2 ton status

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    Hey, that makes sense.
    I went out and did it.
    Someone please idiot test me and make sure I'm reading my multimeter right. All I usually do is check for 12V dc.

    Ok, I set the digital multimeter on mA DC (little m.)
    There were three range selections : 2m, 20m and 200m.
    I put it on the middle one, 20m.
    With the positive wire off, I hooked my meter between the positive battery cable and the positive post on the battery.
    With nothing on, the LCD showed 0.34 (again, on the 20m range.)
    WIth the dome light turned on (door open) it went to somethign like 3.2 or 3.7, something like that.
    So, my reading is..... 0.34 mA with nothing on.... right? Maybe I'm just tired, or am I supposed to carry the decimal and it would be 340 mA...
    I double checked my post, and the range and output is exactly as it was on the multimeter.
    If it helps, the only thing I SHOULD have as a cont. draw is my radio presets on my cheapo cassette deck. I don't think the MSD draws anything unless the ign hot is on.
    Thanks for the help!
    -- Mike
     
  6. Skigirl

    Skigirl 1/2 ton status

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    If there's no drain, I think that your radio presets would pull more than .34 mA. I think your reading there is 3.4 with the meter set to 20.

    My meter shows about the same when there's nothing drawing. But it jumps to about 190 mA when I open the doors - when I have the meter setting at 200mA.

    Test it at the 200mA setting so you can be sure of the reading and in case I have the same brain fart happening.
     
  7. TX Mudder

    TX Mudder 1/2 ton status

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    Ok, I figured the multimeter out. The 20mA setting is ALSO the 10A satting depending on which plug you put the red wire in.
    I am drawing 340 mA at rest. No good. I will try the pull one fuse at a time trick when I have some daylight. I already tried a few.
    Skigirl - I read that you had bad doorjam switches. I recently replaced mine, but who knows. How did you test them?
    -- Mike
     
  8. Skigirl

    Skigirl 1/2 ton status

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    Yikes! /forums/images/graemlins/eek.gif 340 mA... worse than what I had.

    I found my switch problem by accident - by taking a bolt and wedging it between the door jamb switch and the body with the door open. The drain went away (at least for that day...it came back in other places). If you pull the door switch out (it just unscrews) then pull the wire off the switch and retest, that should rule the switch out or confirm.

    I chased the drain in mine around til I got tired of it and put in a battery disconnect. I lose my radio presets, but until I decide to pursue it again, it's totally worth it.
     
  9. TX Mudder

    TX Mudder 1/2 ton status

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    I have gone through and pulled each fuse with no change - approx 350 mA draw.
    I removed the door jamb switch and taped them off. I removed the horn button ground. I disconnected the lighter hot.
    Still, I have the draw.

    Just what all else is there that could be drawing that isn't fused???

    Does anyone have some ideas? I don't mind taking the take the drag the multimeter around the truck, but I'm not sure where else to look.

    I'm thinking about removing the instrument cluster to see if that does anything, p lus I'd have bveen access to underdash wiring that way, but that's a bit of extra work that could prove to be pointless.
    Someone throw me a bone!
    -- Mike
     
  10. Skigirl

    Skigirl 1/2 ton status

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    Sounds like a replay of my recent life. If you've added components and discovered the drain afterwards, those components may be a problem.

    I also had fuses under the hood.

    Switches can cause the problem too (headlights, for example).

    I will say, tho, after chasing mine for a month, checking all fuses, looking at all wires I could see, chasing the drain from the door jamb, to the stereo head unit, to the ham radio antenna, to the ham radio itself, I put in a battery disconnect and gave myself a break. I still haven't found it, and tho I am determined to do so eventually, I didn't want to deal with the trashed battery thing all the time.

    My suggestion: put in a disconnect now, then keep looking. It takes the desperation out of it.
     
  11. TX Mudder

    TX Mudder 1/2 ton status

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    Do you have to pop the hood everytime to disconnect/reconnect? Or is it somehow accessible through the grill?
    Did you buys yours through JEGS or from a local auto parts chain or...?
    I that that's a good idea. I don't even want to drive it because of what a PITA it is.
    -- Mike
     
  12. Skigirl

    Skigirl 1/2 ton status

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    I bought an all metal housed disconnect made by Taylor, from a local parts store (PAW). Probably overpaid for it too, but I wanted one right away. I think LMC has one with a key that you can remove (so there's some theft protection too), but I think it's a plastic housing and a lot cheaper than the one I got.

    I mounted mine inside the cab, on the pass side metal part of the dash, between the glove box and the pass side door. I put it there because it made for a shorter run of battery cable (negative) and there was a fair amount of space there. I didn't want to raise the hood all the time...way too much of a PITA. Just drilled thru the firewall, ran welded cable inside a loom.

    I'll post pics if you'd like.
     

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